ASE Automobile (A1–A8) — All Questions

A cylinder head is warped beyond specification. Which service is normally required to restore a flat sealing surface?

• a.Retorquing the head while hot
• b.Replacing the head bolts only
• c.Resurfacing (machining) the head✓
• d.Installing a thicker head gasket

A warped head must be resurfaced by machining to bring the deck within flatness specification. A thicker gasket will not correct an uneven surface, and simply retorquing does not remove the warp. Excessive material removal, however, can raise compression and change valve timing on some engines.

Technician A says a blown head gasket can allow coolant to enter a cylinder and cause white exhaust smoke. Technician B says it can cause bubbles in the coolant recovery tank from combustion gases. Who is correct?

• a.Technician A only
• b.Technician B only
• c.Both A and B✓
• d.Neither A nor B

A failed head gasket can leak both ways: coolant into the cylinder produces white steam-like exhaust, and combustion pressure into the cooling system produces bubbles and possible overheating. Both technicians describe valid symptoms. A cooling-system pressure test and a combustion-gas (block) test help confirm the diagnosis.

A valve that fails to seat fully will most directly cause which condition?

• a.High oil pressure
• b.Low cylinder compression on that cylinder✓
• c.Excessive oil consumption only
• d.A stuck lifter

A valve that does not seat allows combustion pressure to escape, lowering compression in that cylinder and often causing a misfire. A cylinder leak-down test with air hissing from the intake or exhaust confirms an intake or exhaust valve leak. Burned valves and carbon deposits are common causes.

On an overhead-cam engine, excessive valve lash (clearance) most commonly produces which symptom?

• a.Low oil pressure
• b.A clicking or tapping noise from the valvetrain✓
• c.Blue exhaust smoke
• d.Loss of coolant

Too much clearance in the valvetrain lets components hammer against one another, producing a rhythmic tapping that changes with engine speed. Insufficient lash, by contrast, can hold valves open and burn them. Proper adjustment restores quiet operation and correct valve timing.

Technician A says the PCV system routes crankcase blow-by vapors into the intake to be burned. Technician B says a stuck PCV valve can cause rough idle or oil leaks. Who is correct?

• a.Technician B only
• b.Both A and B✓
• c.Technician A only
• d.Neither A nor B

The PCV system draws blow-by gases into the intake so they are burned rather than vented, and a stuck valve can cause rough idle, oil leaks, or high oil consumption. Both technicians are correct. This reduces sludge formation and emissions.

A mechanic measures cylinder taper by comparing bore diameter at the top of ring travel to the bottom. This measurement is taken with a:

• a.Feeler gauge
• b.Compression tester
• c.Dial bore gauge or inside micrometer✓
• d.Vacuum gauge

Cylinder taper and out-of-round are measured with a dial bore gauge or inside micrometer at several points in the bore. Wear is greatest at the top of ring travel where combustion heat and pressure are highest. Excessive taper requires boring and oversize pistons.

Technician A says low oil pressure only at idle on a high-mileage engine can be caused by worn bearing clearances. Technician B says a worn oil pump or diluted oil can also lower pressure. Who is correct?

• a.Both A and B✓
• b.Technician A only
• c.Technician B only
• d.Neither A nor B

Worn bearing clearances let oil escape faster than the pump maintains pressure at low speed, and a worn pump or fuel-diluted oil reduces pressure as well. Both technicians are correct. Verify with a mechanical gauge before condemning parts.

Which cooling-system component regulates coolant flow based on engine temperature?

• a.Heater core
• b.Radiator cap
• c.Thermostat✓
• d.Water pump

The thermostat stays closed until the engine reaches operating temperature, then opens to allow coolant to circulate through the radiator. A stuck-closed thermostat causes overheating; a stuck-open one causes slow warm-up and poor heater output. It is a common, inexpensive cause of temperature complaints.

A radiator pressure cap raises the system's boiling point primarily because:

• a.It adds antifreeze to the coolant
• b.It lowers the coolant level
• c.It speeds up the water pump
• d.Increased pressure raises the coolant's boiling temperature✓

Sealing the system under pressure raises the boiling point of the coolant, allowing higher operating temperatures without boil-over. A weak or faulty cap lowers the effective boiling point and can cause coolant loss. Caps should be pressure-tested when overheating is suspected.

Blue smoke from the exhaust under acceleration most often indicates:

• a.A lean misfire
• b.A rich fuel mixture
• c.Coolant in the combustion chamber
• d.Oil entering the combustion chamber✓

Blue smoke indicates oil is being burned, commonly from worn rings, cylinder walls, or valve guide seals. White smoke suggests coolant, and black smoke suggests excess fuel. A leak-down or compression test helps localize the source.

Technician A says timing-chain stretch can retard valve timing and set a camshaft/crankshaft correlation code. Technician B says a stretched timing chain has no effect on engine performance. Who is correct?

• a.Both A and B
• b.Technician B only
• c.Neither A nor B
• d.Technician A only✓

A stretched or worn timing chain changes the relationship between crankshaft and camshaft position, retarding valve timing and often setting a correlation DTC. This can cause rough running and reduced power. Technician B is incorrect because timing is directly affected.

Head bolts that use a torque-to-yield (TTY) design should be:

• a.Coated with anti-seize before reuse
• b.Replaced with new bolts during reassembly✓
• c.Reused indefinitely
• d.Torqued to half the final value only

Torque-to-yield bolts are stretched into their plastic range for a uniform clamp load and should not be reused. Reusing them risks uneven clamping and gasket failure. Always follow the specified torque-plus-angle sequence with new bolts.

The main function of engine oil, besides lubrication, includes all of the following EXCEPT:

• a.Generating spark for combustion✓
• b.Cleaning and suspending contaminants
• c.Sealing between rings and cylinder walls
• d.Cooling internal components

Engine oil lubricates, cools, cleans, and helps seal the rings, but it plays no role in generating spark. Spark is produced by the ignition system. Detergent and dispersant additives keep contaminants suspended until the filter or an oil change removes them.

A rhythmic knocking noise that is loudest under load and disappears when one cylinder is disabled most likely indicates:

• a.A loose accessory belt
• b.A worn connecting-rod bearing on that cylinder✓
• c.A sticking valve
• d.An exhaust leak

A rod bearing knock is load-sensitive and typically quiets when that cylinder's contribution is removed by disabling its injector or spark. Loose belts and exhaust leaks make different noises unrelated to individual cylinders. Excessive rod bearing clearance is confirmed with Plastigage during disassembly.

Coolant is leaking internally and the engine oil appears milky. The MOST likely cause is:

• a.A worn timing belt
• b.A failed head gasket or cracked block/head✓
• c.A clogged air filter
• d.A stuck thermostat

A milky, tan appearance in the oil indicates coolant contamination, commonly from a head gasket failure or a crack that connects a coolant passage to the oil. Continued operation damages bearings. Pressure and combustion-gas testing help pinpoint the leak path.

Before final assembly, plastigage is used to measure:

• a.Piston ring end gap
• b.Valve spring free length
• c.Bearing oil clearance✓
• d.Cylinder bore taper

Plastigage is a crushable plastic thread that indicates bearing oil clearance when compared to a scale after the cap is torqued. Ring end gap is measured with a feeler gauge in the bore, and bore taper with a bore gauge. Correct clearance is essential for oil film and bearing life.

In an automatic transmission, the torque converter's function is to:

• a.Engage the parking pawl
• b.Couple the engine to the transmission and multiply torque✓
• c.Generate line pressure directly
• d.Cool the engine oil

The torque converter is a fluid coupling that transmits power from the engine to the transmission and multiplies torque during acceleration. Its lockup clutch mechanically links the engine and transmission at cruise to improve fuel economy. The pump, not the converter, generates line pressure.

Technician A says burnt-smelling, dark automatic transmission fluid can indicate overheating and clutch damage. Technician B says fluid color and smell never matter. Who is correct?

• a.Technician B only
• b.Both A and B
• c.Neither A nor B
• d.Technician A only✓

Dark, burnt-smelling ATF indicates overheating and worn friction material from slipping clutches or bands. Healthy fluid is typically red and translucent. Technician B is wrong because fluid condition is an important diagnostic clue.

A manual transmission clutch that slips under load, especially in higher gears, most commonly indicates:

• a.Too much clutch pedal free play
• b.A broken motor mount
• c.A dry pilot bearing
• d.A worn clutch disc or weak pressure plate✓

A worn friction disc or weak pressure plate cannot hold torque, so the clutch slips under load and engine rpm rises without matching acceleration. Slipping generates heat that accelerates wear. Insufficient free play, not too much, can also cause slipping.

Constant-velocity (CV) joints are used on front-wheel-drive axles primarily because they:

• a.Transmit power smoothly through varying steering angles✓
• b.Are cheaper than U-joints
• c.Require no lubrication
• d.Eliminate the need for a differential

CV joints deliver constant rotational speed while the axle operates through the wide angles created by steering and suspension travel. A torn CV boot lets grease escape and dirt enter, leading to a clicking noise during turns. Boot inspection is a routine maintenance check.

A clicking noise from the front of a FWD vehicle that increases when turning sharply is most likely caused by:

• a.A worn outer CV joint✓
• b.An unbalanced tire
• c.A leaking transmission seal
• d.A worn wheel bearing

A worn outer CV joint clicks under the load of a sharp turn, and the noise usually worsens with steering angle. A torn boot that allowed grease loss is a frequent cause. Wheel bearing noise, by contrast, is typically a steady drone that changes with vehicle speed.

The differential in a rear axle allows:

• a.The transmission to shift gears
• b.The drive wheels to rotate at different speeds during turns✓
• c.The driveshaft to change length
• d.The engine to idle smoothly

The differential splits torque to the drive wheels while allowing them to turn at different speeds when cornering, since the outer wheel travels farther. A limited-slip design adds resistance to reduce wheel spin. Whining or howling noises often indicate worn or improperly set-up gears.

Technician A says a worn driveshaft U-joint can cause a clunk on acceleration. Technician B says it can cause a vibration that increases with vehicle speed. Who is correct?

• a.Neither A nor B
• b.Technician A only
• c.Both A and B✓
• d.Technician B only

A worn universal joint clunks when torque is applied and vibrates more as speed rises because the joint develops play. Both technicians describe valid symptoms. Rust-colored dust around the caps is an early sign of failure.

A vehicle has a final drive ratio of 3.73:1. This means the:

• a.Driveshaft turns 3.73 times for each wheel revolution✓
• b.Engine turns at 3.73 percent of wheel speed
• c.Transmission has 3.73 forward gears
• d.Wheels turn 3.73 times per driveshaft revolution

A 3.73:1 final drive means the driveshaft (ring-and-pinion input) turns 3.73 times for every one revolution of the axle/wheel. A numerically higher ratio improves acceleration but raises cruising rpm. Ratio is found by dividing ring-gear teeth by pinion-gear teeth.

Technician A says most dipstick-equipped automatics are checked with the engine running at operating temperature. Technician B says fluid level is unaffected by temperature. Who is correct?

• a.Technician B only
• b.Neither A nor B
• c.Technician A only✓
• d.Both A and B

Dipstick-equipped automatics are checked hot with the engine running and the selector cycled, and fluid expands with temperature so the reading depends on it. Technician B is wrong. Many modern units use a sealed fill within a specified fluid-temperature window.

Technician A says a slipping band or clutch pack can cause delayed or harsh shifts. Technician B says low line pressure can cause slipping and overheating. Who is correct?

• a.Both A and B✓
• b.Technician A only
• c.Technician B only
• d.Neither A nor B

Worn friction elements slip and cause delayed, harsh, or flaring shifts, while low line pressure reduces clamping force and leads to slippage and heat. Both conditions are valid causes of shift complaints. A pressure test and scan-tool data help isolate the fault.

Excessive clutch pedal free play in a manual transmission can cause:

• a.Loss of transmission fluid
• b.The flywheel to warp
• c.Incomplete clutch release, making shifting difficult✓
• d.The clutch to slip under load

Too much free play prevents the clutch from fully disengaging, causing grinding or hard shifting because the disc still contacts the flywheel. Too little free play causes slipping. Hydraulic systems self-adjust, while cable systems may require manual adjustment.

A gear ratio is calculated by dividing the number of teeth on the driven gear by the number on the drive gear. A drive gear with 12 teeth turning a driven gear with 36 teeth produces a ratio of:

• a.2:1
• b.3:1✓
• c.4:1
• d.1:3

Dividing 36 driven teeth by 12 drive teeth gives a 3:1 reduction, meaning the drive gear turns three times for each output revolution. This multiplies torque while reducing speed. Understanding ratios is essential for diagnosing driveline gearing and speedometer calibration.

A whining noise from an automatic transmission that changes with engine speed but is present in Park and Neutral most likely points to:

• a.A slipping clutch pack
• b.A worn output shaft bearing
• c.A worn CV joint
• d.A failing transmission fluid pump✓

Because the pump is driven by the converter hub whenever the engine runs, a pump-related whine is present in Park and Neutral and varies with engine rpm. Output-related noises appear only when the vehicle moves. Low fluid or aeration can produce similar sounds.

The pilot bearing or bushing in a manual-transmission vehicle supports the:

• a.Throwout bearing
• b.Tip of the transmission input shaft✓
• c.Flywheel ring gear
• d.Clutch release fork

The pilot bearing supports the front tip of the input shaft in the end of the crankshaft, keeping it centered. A worn pilot bearing causes noise and hard shifting, especially with the clutch depressed. It should be inspected or replaced whenever the clutch is serviced.

Camber angle is defined as the:

• a.Inward or outward tilt of the wheel from vertical, viewed from the front✓
• b.Difference in toe between left and right wheels
• c.Forward or rearward tilt of the steering axis
• d.Angle of the tie rod to the ground

Camber is the inward (negative) or outward (positive) tilt of the wheel from true vertical when viewed from the front. Incorrect camber causes uneven tire wear on one shoulder and can pull the vehicle to one side. It is adjusted where the suspension design allows.

Excessive positive caster generally results in:

• a.Wander at highway speed
• b.Rapid center-tread wear
• c.Loss of directional stability
• d.Increased steering effort but improved straight-line stability✓

Positive caster tilts the steering axis rearward at the top, improving straight-line stability and steering return but increasing effort. Too little caster causes wander and poor return. Caster is measured during alignment and typically compared side to side.

Toe refers to the:

• a.Height of the vehicle at the fender
• b.Vertical tilt of the wheel
• c.Rearward tilt of the steering axis
• d.Difference in distance between the front and rear of a pair of tires, viewed from above✓

Toe is the difference between the leading and trailing edges of the tires viewed from above; toe-in means the fronts are closer together. Incorrect toe is the leading cause of rapid, feathered tire wear. It is the most critical alignment angle for tire life and is always adjustable.

A tire worn on both inner and outer edges, with good tread in the center, most likely indicates:

• a.Over-inflation
• b.Excessive positive camber
• c.Chronic under-inflation✓
• d.A worn tie rod end

Under-inflation lets the tire ride on both shoulders while the center bears less load, wearing both edges. Over-inflation does the opposite, wearing the center. Correct inflation and periodic pressure checks prevent this pattern.

Technician A says a worn tie rod end can cause a toe change and tire wear. Technician B says it can cause excessive play in the steering and a failed alignment. Who is correct?

• a.Both A and B✓
• b.Technician B only
• c.Neither A nor B
• d.Technician A only

A worn tie rod end introduces play that changes toe as the wheel moves, causing wandering and feathered tire wear, and it will prevent a stable alignment. Both technicians are correct. Worn steering and suspension parts must be replaced before performing an alignment.

Technician A says worn shocks or struts can cause the body to keep bouncing after a bump. Technician B says worn dampers have no effect on tire wear. Who is correct?

• a.Both A and B
• b.Technician A only✓
• c.Neither A nor B
• d.Technician B only

Worn shocks lose their ability to dampen spring oscillation, so the body keeps bouncing after a bump, and weak dampers also cause tire cupping. Technician B is wrong because damper wear does affect tire wear. A bounce test and leak inspection confirm the condition.

Cupping or scalloping tire wear is most commonly associated with:

• a.Worn suspension dampers or unbalanced wheels✓
• b.Excessive toe-in
• c.A slipping clutch
• d.Over-torqued lug nuts

Cupping, a series of dips around the tread, results from the tire bouncing due to worn shocks/struts or from imbalance. It usually comes with a noise that changes with speed. Correcting the damper or balance issue and rotating tires helps.

The purpose of a stabilizer (sway) bar is to:

• a.Support the full weight of the vehicle
• b.Adjust ride height
• c.Absorb road shock like a shock absorber
• d.Reduce body roll during cornering✓

The stabilizer bar links the left and right suspension to resist body lean when cornering, improving handling. Worn sway bar links or bushings produce a rattle or clunk over bumps. It does not carry ride height or primary spring load.

Technician A says a side-to-side camber difference can cause a vehicle to pull toward the more positive side. Technician B says a defective tire can also cause a pull. Who is correct?

• a.Neither A nor B
• b.Technician B only
• c.Both A and B✓
• d.Technician A only

A cross-camber difference pulls the vehicle toward the more positive side, and a defective (conicity) tire can pull as well. Both technicians are correct. Compare cross-camber and cross-caster and swap tires side to side to isolate a tire pull.

In a power rack-and-pinion steering system, increased steering effort in only one direction most likely indicates:

• a.A bent stabilizer bar
• b.An internal leak or valve fault in the steering gear✓
• c.A low battery
• d.A worn wheel bearing

Effort that is heavy in one direction points to an internal fault such as worn seals or a control valve problem that fails to direct assist correctly. Uniformly hard steering suggests low fluid or a pump/belt issue. Electric power steering faults set codes and can be scanned.

The included angle in an alignment is the sum of:

• a.Toe and camber
• b.Caster and toe
• c.Camber and steering axis inclination (SAI)✓
• d.Caster and SAI

Included angle equals camber plus SAI and is useful for detecting bent spindles or struts, since SAI is built in and not adjustable. If included angle differs side to side, a component is likely bent. It is a diagnostic angle rather than an adjustable one.

A steering wheel that is off-center after an alignment, though the vehicle tracks straight, usually indicates:

• a.Improperly set toe split between the two front wheels✓
• b.A weak spring
• c.Excessive camber
• d.A worn wheel bearing

When total toe is correct but not divided equally between the wheels, the steering wheel sits off-center even though the vehicle goes straight. Centering the steering and re-setting individual toe corrects it. This is checked with the steering wheel locked in the centered position.

Technician A says tires should be rotated to promote even wear. Technician B says the tire's load index and speed rating should meet or exceed the vehicle's requirements. Who is correct?

• a.Neither A nor B
• b.Technician B only
• c.Both A and B✓
• d.Technician A only

Rotation evens out the different wear rates at each position, and replacement tires must meet the vehicle's load and speed ratings for safe operation. Both statements are correct service practice. Always follow the recommended rotation pattern for the drivetrain type.

Technician A says a worn ball joint can cause clunking, wander, and uneven tire wear. Technician B says a load-carrying ball joint should be checked with its load removed per the procedure. Who is correct?

• a.Both A and B✓
• b.Technician A only
• c.Neither A nor B
• d.Technician B only

A worn ball joint clunks, wanders, and wears tires unevenly, and load-carrying joints are checked unloaded so the measured axial and radial play is accurate. Both technicians are correct. A worn ball joint can fail catastrophically if ignored.

The main purpose of a wheel alignment is to:

• a.Adjust the brakes
• b.Set suspension angles for proper handling and even tire wear✓
• c.Increase engine power
• d.Balance the wheels

Alignment sets camber, caster, and toe so the tires meet the road correctly, giving good handling, steering return, and even tire wear. Balancing is a separate operation addressing weight distribution. Worn parts must be repaired before alignment angles will hold.

Wheel/tire imbalance is most often felt as:

• a.A vibration that appears at a particular speed✓
• b.Hard steering at low speed
• c.A pull to one side
• d.A grinding noise when braking

An out-of-balance wheel creates a vibration that emerges at a specific speed as the heavy spot spins. Static and dynamic balancing corrects it by adding weights. A pull, by contrast, is usually an alignment or tire construction issue.

A brake pedal that slowly sinks to the floor while held under steady pressure most likely indicates:

• a.Glazed brake pads
• b.A failing master cylinder (internal leak)✓
• c.Warped rotors
• d.Air in the lines only

A pedal that gradually falls under steady pressure indicates fluid bypassing internally in the master cylinder past worn seals. An external leak would lose fluid visibly. Replacing the master cylinder and bleeding the system restores a firm pedal.

Technician A says a spongy brake pedal is commonly caused by air in the hydraulic system. Technician B says air in the lines increases braking power. Who is correct?

• a.Neither A nor B
• b.Both A and B
• c.Technician B only
• d.Technician A only✓

Air is compressible, so it makes the pedal feel soft or spongy and reduces braking effectiveness; proper bleeding removes it. Technician B is wrong because air degrades rather than improves braking. Bleeding in the correct sequence restores a firm pedal.

Technician A says a pulsating brake pedal is usually caused by air in the hydraulic lines. Technician B says it is usually caused by rotor thickness variation or excessive lateral runout. Who is correct?

• a.Neither A nor B
• b.Technician A only
• c.Both A and B
• d.Technician B only✓

Thickness variation or warp causes the pads to move in and out as the disc turns, producing a pulsation felt in the pedal, while air produces a soft pedal instead. Technician B is correct. Measuring runout and thickness variation confirms it.

The primary purpose of a brake power booster is to:

• a.Store brake fluid
• b.Adjust the parking brake
• c.Prevent wheel lockup
• d.Reduce the pedal effort required to apply the brakes✓

The vacuum or hydraulic booster multiplies the driver's pedal force so less effort is needed for firm braking. A failed vacuum booster or leaking check valve produces a hard pedal. It works with, not instead of, the hydraulic system.

The main function of an anti-lock brake system (ABS) is to:

• a.Eliminate the need for brake pads
• b.Replace the parking brake
• c.Prevent wheel lockup and maintain steering control during hard braking✓
• d.Increase brake fluid pressure permanently

ABS pulses hydraulic pressure to keep wheels from locking so the driver retains steering control and shortens stopping distance on most surfaces. Wheel-speed sensors feed the control module, which modulates the hydraulic unit. A fault typically turns on the ABS warning lamp and disables the function.

A wheel-speed sensor signal that is missing on one wheel will most likely cause the ABS to:

• a.Lock all four wheels
• b.Increase engine power
• c.Set a code and disable ABS, reverting to normal braking✓
• d.Apply the parking brake

A lost wheel-speed signal sets a DTC and usually disables ABS, leaving conventional (non-anti-lock) braking available. The ABS warning lamp illuminates. Common causes include a damaged sensor, wiring, or a contaminated tone ring.

Brake fluid is hygroscopic, which means it:

• a.Repels all water
• b.Absorbs moisture from the air over time✓
• c.Expands when frozen
• d.Conducts electricity

Glycol-based brake fluid absorbs moisture, which lowers its boiling point and can cause corrosion and a spongy pedal from vapor under heavy braking. This is why periodic fluid replacement is recommended. Sealed containers and prompt cap replacement limit moisture uptake.

During a disc brake job, a technician should measure rotor thickness and compare it to the:

• a.Toe specification
• b.Tire pressure specification
• c.Minimum (discard) thickness stamped on the rotor✓
• d.Battery voltage

Rotors must remain above the minimum thickness (often cast or stamped on the rotor) to dissipate heat and resist warping. A rotor below spec must be replaced, not machined. Measuring with a micrometer at several points also reveals thickness variation.

Technician A says brake shoes are used in disc brakes. Technician B says brake shoes are used in drum brakes. Who is correct?

• a.Neither A nor B
• b.Both A and B
• c.Technician B only✓
• d.Technician A only

Drum brakes use curved shoes that press outward against the drum, while disc brakes use flat pads that clamp a rotor. Technician B is correct. Many vehicles combine front discs with rear drums or discs.

Technician A says a grinding, metal-on-metal noise during braking indicates friction material worn past its limit. Technician B says continued driving in that condition can score the rotor or drum. Who is correct?

• a.Technician B only
• b.Neither A nor B
• c.Technician A only
• d.Both A and B✓

When friction material wears away, the metal backing contacts the rotor or drum, producing a grinding noise, and continued driving scores the surface and raises repair cost. Both technicians are correct. Immediate pad or shoe replacement and surface inspection are required.

A rear disc parking brake that will not hold is often caused by:

• a.A misadjusted or seized parking brake mechanism/cable✓
• b.Air in the front lines
• c.Low battery voltage
• d.A failed wheel-speed sensor

Parking brake holding faults usually trace to cable stretch, misadjustment, or a seized caliper parking mechanism. Proper adjustment and lubrication restore holding force. On integral rear calipers, the internal actuator must function for both service and parking braking.

A brake caliper that sticks and does not release will most likely cause:

• a.A hard pedal at all times
• b.Dragging, overheating, and pulling to that side✓
• c.A soft pedal only
• d.Loss of all braking

A seized caliper keeps the pads applied, causing drag, excessive heat, uneven pad wear, and a pull toward that wheel. Overheated fluid can boil and reduce braking. Rebuilding or replacing the caliper and inspecting the slides and hose corrects it.

The metering valve in a combination valve is used to:

• a.Warn of ABS faults
• b.Bleed the master cylinder
• c.Increase rear brake pressure
• d.Delay front disc application so rear drums engage together✓

The metering valve holds off front disc pressure briefly so the rear drum shoes overcome their return springs and apply at nearly the same time, balancing braking. The proportioning section limits rear pressure to prevent lockup. Together these balance front-to-rear braking.

When bleeding a conventional hydraulic brake system, the general rule is to bleed:

• a.Only the front wheels
• b.All wheels at the same time
• c.In the sequence specified by the manufacturer, often longest line first✓
• d.Starting at the wheel nearest the master cylinder

Manufacturers specify a bleeding sequence, frequently starting at the wheel farthest from the master cylinder, to purge air effectively. Following the correct order and keeping the reservoir full prevents introducing more air. Some ABS units require a scan tool to bleed fully.

A proportioning valve in the brake system is designed to:

• a.Store extra brake fluid
• b.Reduce pressure to the rear brakes to prevent early lockup✓
• c.Increase pressure to the front only
• d.Operate the parking brake

Because weight shifts forward during braking, the proportioning valve limits rear brake pressure to keep the rear wheels from locking prematurely. This maintains stability during hard stops. Many vehicles now handle this function electronically through ABS/EBD.

Technician A says silicone (DOT 5) and glycol (DOT 3/4) brake fluids can be freely mixed. Technician B says brake fluid type is unimportant. Who is correct?

• a.Technician B only
• b.Both A and B
• c.Technician A only
• d.Neither A nor B✓

Silicone and glycol fluids are not compatible and must not be mixed, and using the wrong fluid type can damage seals and reduce performance. Both technicians are incorrect. Always use the fluid specification listed for the vehicle.

Using Ohm's law, a 12-volt circuit with 4 ohms of resistance will carry a current of:

• a.3 amps✓
• b.16 amps
• c.0.33 amps
• d.48 amps

Ohm's law states current equals voltage divided by resistance, so 12 volts divided by 4 ohms equals 3 amps. Understanding this relationship is essential for diagnosing circuit faults. Higher resistance in a circuit reduces current flow for a given voltage.

Technician A says a voltage-drop test across a battery cable can reveal unwanted resistance. Technician B says a voltage-drop test is more accurate than a visual inspection for finding poor connections. Who is correct?

• a.Technician A only
• b.Neither A nor B
• c.Technician B only
• d.Both A and B✓

A voltage-drop test measures the voltage lost across a connection under load, so high drop reveals corrosion or loose connections that a visual check may miss. Both technicians are correct. Acceptable drop is typically a few tenths of a volt or less.

A fully charged 12-volt lead-acid battery at rest should read approximately:

• a.13.8 volts
• b.11.8 volts
• c.10.5 volts
• d.12.6 volts✓

A healthy, fully charged 12-volt battery reads about 12.6 volts open-circuit at rest. Around 12.4 is roughly 75 percent, and 12.0 is about 25 percent charged. A surface charge should be removed before testing for accuracy.

Technician A says the charging system voltage at the battery with the engine running should typically be around 13.5 to 14.5 volts. Technician B says it should read exactly 12.6 volts while running. Who is correct?

• a.Technician A only✓
• b.Technician B only
• c.Both A and B
• d.Neither A nor B

With the engine running, the alternator should raise system voltage to roughly 13.5 to 14.5 volts to charge the battery and run loads. A reading of 12.6 running would indicate the charging system is not working. Technician B describes a resting, not charging, voltage.

Two 6-ohm resistors connected in parallel produce a total resistance of:

• a.6 ohms
• b.12 ohms
• c.0.5 ohms
• d.3 ohms✓

For two equal resistors in parallel, total resistance is half of one resistor, so two 6-ohm resistors equal 3 ohms. Parallel resistance is always lower than the smallest branch. This principle explains why adding parallel loads increases total current draw.

An open in a series circuit will cause:

• a.Higher voltage at the load
• b.Increased current flow
• c.No current flow in the circuit✓
• d.Reduced resistance

A series circuit has only one path, so an open anywhere stops all current and the load will not operate. Voltage will be present up to the open point when tested. Locating the open often uses a test light or voltmeter along the circuit.

A starter that cranks slowly, with the battery known good and fully charged, most likely has:

• a.A weak alternator
• b.A blown headlight fuse
• c.High resistance in the starter circuit or a failing starter✓
• d.Too little engine oil

Slow cranking with a good battery points to high resistance in the cables/connections or a worn starter, both of which limit current to the motor. A starter-circuit voltage drop test isolates the problem. Clean, tight connections are essential for full cranking current.

Power (watts) in an electrical circuit is calculated by:

• a.Voltage multiplied by current✓
• b.Voltage divided by resistance
• c.Resistance multiplied by voltage
• d.Current divided by voltage

Electrical power equals voltage times current (P = E x I). A 12-volt circuit drawing 5 amps consumes 60 watts. This relationship helps size fuses, wiring, and components for their load.

A parasitic (key-off) battery drain is measured by connecting an ammeter:

• a.In series between a battery terminal and the cable✓
• b.In parallel across the battery terminals
• c.Across a spark plug
• d.Between two ground points

Parasitic draw is measured by placing an ammeter in series in the battery circuit after modules go to sleep. Excessive draw discharges the battery overnight. Pulling fuses one at a time while watching the meter isolates the offending circuit.

In a wiring diagram, a component shown connected to ground provides:

• a.Signal amplification
• b.Fuse protection
• c.The return path for current back to the battery negative✓
• d.The source of voltage

Ground is the return path that completes the circuit back to the battery's negative terminal. A poor ground raises resistance and causes dim lights, erratic operation, or feedback. Diagrams use ground symbols to trace current return paths.

Technician A says a fuse that blows again immediately after replacement indicates a short to ground or an overload. Technician B says repeatedly replacing the fuse will fix the circuit. Who is correct?

• a.Both A and B
• b.Technician B only
• c.Technician A only✓
• d.Neither A nor B

A fuse that blows again immediately is protecting the circuit from a short to ground or an overload drawing excess current. Technician B is wrong because the underlying fault, not the fuse, must be repaired. Inspect the wiring for chafing and test the component.

Technician A says a diode allows current to flow in only one direction. Technician B says alternators use diodes to rectify AC into DC. Who is correct?

• a.Technician A only
• b.Both A and B✓
• c.Neither A nor B
• d.Technician B only

A diode conducts in one direction only, and the alternator's diode (rectifier) bridge converts the stator's AC into the DC the vehicle uses. Both statements are correct. A shorted or open diode causes low output and AC ripple on the charging system.

Excessive AC ripple voltage measured at the battery with the engine running usually indicates:

• a.One or more failed alternator diodes✓
• b.A stuck thermostat
• c.A weak starter
• d.A blown headlight bulb

Failed rectifier diodes let AC leak through, producing measurable ripple and reduced DC output. A meter set to AC volts or an oscilloscope reveals it. This often causes charging complaints and can disturb electronic modules.

Technician A says a relay lets a small control current switch a larger load. Technician B says relays protect switches and allow smaller control wiring. Who is correct?

• a.Both A and B✓
• b.Neither A nor B
• c.Technician A only
• d.Technician B only

A relay uses a low-current coil to close contacts that carry a high-current load, which protects switches and permits smaller control wiring. Both technicians are correct. Common uses include headlights, fuel pumps, and cooling fans.

Dim headlights that brighten when engine rpm increases most likely indicate:

• a.A shorted headlight switch
• b.A blown fuse
• c.An open ground on one lamp
• d.A weak battery or undercharging condition✓

Lights that brighten with rpm suggest the charging system is barely keeping up, so a weak battery or low alternator output is likely. A charging system test measures output under load. A high-resistance connection can also dim lights but usually affects specific circuits.

A voltmeter is connected how, relative to the component being tested?

• a.After removing the fuse
• b.Between the two battery posts only
• c.In series with the load
• d.In parallel (across) the component✓

A voltmeter is connected in parallel across the component or connection to measure the voltage difference, since it has very high internal resistance. An ammeter, by contrast, connects in series. Connecting a voltmeter in series would give an incorrect reading.

The gauge or module that displays engine coolant temperature relies on a sensor whose resistance:

• a.Changes with temperature (a thermistor)✓
• b.Produces AC voltage
• c.Stays constant regardless of temperature
• d.Only works above 200 degrees

Most coolant temperature sensors are thermistors whose resistance falls as temperature rises (negative temperature coefficient). The computer or gauge interprets this changing resistance as temperature. A faulty sensor can cause inaccurate readings and driveability or fan-control problems.

A circuit has 12 volts applied and draws 2 amps. Its total resistance is:

• a.6 ohms✓
• b.2 ohms
• c.24 ohms
• d.0.17 ohms

By Ohm's law, resistance equals voltage divided by current, so 12 volts divided by 2 amps equals 6 ohms. Rearranging Ohm's law lets a technician solve for any unknown value. Verifying calculated resistance against measured values helps confirm circuit condition.

In an automotive A/C system, the compressor's job is to:

• a.Store refrigerant
• b.Absorb moisture from the refrigerant
• c.Raise refrigerant pressure and circulate it through the system✓
• d.Condense refrigerant into a liquid

The compressor pressurizes low-pressure refrigerant vapor and pumps it through the system, raising its temperature and pressure before the condenser. It is the pump that drives the refrigeration cycle. A failed compressor clutch or internal damage stops cooling.

The component that changes high-pressure refrigerant vapor into a liquid by removing heat is the:

• a.Expansion valve
• b.Accumulator
• c.Condenser✓
• d.Evaporator

The condenser, mounted in front of the radiator, rejects heat so the high-pressure vapor condenses into a liquid. Airflow across it is essential; a blocked or dirty condenser causes high pressures and poor cooling. The evaporator, by contrast, absorbs heat inside the vehicle.

The evaporator in the passenger compartment:

• a.Rejects heat to the outside air
• b.Stores excess refrigerant
• c.Absorbs heat from cabin air, cooling it✓
• d.Compresses the refrigerant

As low-pressure liquid refrigerant boils in the evaporator, it absorbs heat from the cabin air blown across it, cooling and dehumidifying the air. A restricted or iced evaporator reduces airflow and cooling. Proper refrigerant charge and airflow keep it working correctly.

Technician A says overcharging an A/C system improves cooling. Technician B says overcharging raises system pressures and can reduce cooling and damage the compressor. Who is correct?

• a.Technician B only✓
• b.Both A and B
• c.Technician A only
• d.Neither A nor B

Overcharging raises high-side pressure, reduces cooling efficiency, and can damage the compressor with liquid slugging. The correct charge, measured by weight, is critical. Technician A is wrong; more refrigerant is not better.

The expansion valve or orifice tube controls:

• a.The flow of refrigerant into the evaporator, causing a pressure drop✓
• b.Compressor speed
• c.Blower motor voltage
• d.Cabin air recirculation

The metering device drops the refrigerant pressure and controls flow into the evaporator, allowing it to boil and absorb heat. A restricted orifice or stuck valve causes poor cooling and abnormal pressures. It separates the high side from the low side of the system.

The desiccant in a receiver-drier or accumulator is used to:

• a.Add oil to the system
• b.Absorb moisture from the refrigerant✓
• c.Increase refrigerant pressure
• d.Cool the condenser

The desiccant removes moisture that would otherwise form acids and ice, protecting the system. It should be replaced whenever the system is opened for major service. Saturated desiccant can break down and contaminate the system.

Technician A says a low refrigerant charge typically shows low readings on both gauges with poor cooling. Technician B says the leak should be repaired before recharging to the correct weight. Who is correct?

• a.Neither A nor B
• b.Technician B only
• c.Both A and B✓
• d.Technician A only

An undercharge shows low readings on both gauges with weak cooling and rapid cycling, and any leak must be repaired before recharging by weight. Both technicians are correct. Dye or an electronic detector locates the leak source.

Technician A says cabin heat comes from engine coolant flowing through the heater core. Technician B says a leaking heater core can fog the windshield and leave a sweet smell. Who is correct?

• a.Neither A nor B
• b.Technician B only
• c.Technician A only
• d.Both A and B✓

The heater core transfers heat from hot engine coolant to cabin air, and a leaking core lets coolant fog the glass and produce a sweet odor. Both technicians are correct. A clogged core or low coolant reduces heat output.

Technician A says a stuck-closed blend-air door can cause no heat even with a good heater core. Technician B says a failed blower motor can cause no airflow from the vents. Who is correct?

• a.Technician B only
• b.Technician A only
• c.Both A and B✓
• d.Neither A nor B

A blend door controls how much air passes over the heater core, so a stuck door can cause no heat, and a failed blower stops airflow entirely. Both technicians are correct. Actuator and door faults are common causes of temperature-control complaints.

Before servicing an A/C system, refrigerant must be:

• a.Mixed with fresh oil
• b.Vented outdoors quickly
• c.Recovered with approved equipment, not vented to the atmosphere✓
• d.Frozen in the condenser

Regulations require recovering refrigerant with certified equipment rather than releasing it, because it is a controlled substance. Recovery, recycling, and recharging equipment protects the environment and allows accurate recharging. Technicians handling refrigerant must be certified.

An A/C compressor clutch that will not engage could be caused by all of the following EXCEPT:

• a.A low-refrigerant lockout from the pressure switch
• b.A clogged cabin air filter✓
• c.A blown clutch fuse or relay
• d.An open clutch coil

The clutch may fail to engage due to a low-charge lockout, electrical faults, or an open coil, but a dirty cabin filter only reduces airflow, not clutch engagement. Diagnosis checks power, ground, and the pressure switches. A cabin filter affects volume, not the refrigerant cycle.

Higher-than-normal readings on both the high and low sides of an A/C system, with poor cooling, could indicate:

• a.A stuck-open thermostat
• b.An overcharge or a condenser airflow/cooling problem✓
• c.An open blower resistor
• d.A low refrigerant charge

High readings on both gauges often point to an overcharge or inadequate condenser cooling from a blocked condenser or inoperative cooling fan. Verifying charge weight and fan operation is the next step. Correcting airflow and charge restores normal pressures.

An oxygen (O2) sensor in the exhaust provides feedback to the PCM about:

• a.Ignition timing advance
• b.Engine oil level
• c.The air-fuel ratio (rich or lean)✓
• d.Coolant temperature

The oxygen sensor measures residual oxygen in the exhaust, telling the PCM whether the mixture is rich or lean so it can adjust fuel trim. A lazy or failed sensor degrades fuel control and emissions. Wide-band sensors report the actual ratio rather than just rich/lean.

A diagnostic trouble code (DTC) of P0301 indicates:

• a.A lean condition on bank 1
• b.An EVAP leak
• c.A faulty coolant sensor
• d.A misfire detected in cylinder number 1✓

P0301 is a cylinder-specific misfire code, with the last digit identifying cylinder 1. P0300 indicates a random/multiple-cylinder misfire. Causes include ignition, fuel, or mechanical (compression) problems in that cylinder.

Technician A says a vacuum leak causes a rich condition. Technician B says a vacuum leak adds unmetered air and causes a lean condition, especially at idle. Who is correct?

• a.Both A and B
• b.Technician B only✓
• c.Technician A only
• d.Neither A nor B

A vacuum leak lets extra air enter after the mass airflow sensor, leaning the mixture and often causing a rough idle and positive fuel trim. Technician B is correct. Smoke testing helps locate intake leaks.

Technician A says a positive long-term fuel trim of +20 percent means the PCM is adding fuel to correct a lean condition. Technician B says positive trim means the engine is running rich. Who is correct?

• a.Both A and B
• b.Technician A only✓
• c.Technician B only
• d.Neither A nor B

Positive fuel trim means the computer is adding fuel to correct a lean condition from a vacuum leak, low fuel pressure, or a dirty MAF. Technician B is wrong because rich conditions produce negative trims. Comparing short- and long-term trims helps pinpoint the fault.

Technician A says a rich air-fuel mixture can raise tailpipe CO and HC. Technician B says the oxygen sensor helps the PCM keep the mixture near stoichiometric. Who is correct?

• a.Both A and B✓
• b.Technician A only
• c.Neither A nor B
• d.Technician B only

A rich mixture leaves excess fuel that raises carbon monoxide and hydrocarbons, and the oxygen sensor feedback lets the PCM hold the mixture near the ideal ratio. Both technicians are correct. A lazy sensor degrades fuel control and emissions.

Technician A says the MAF sensor measures the mass of air entering the engine so the PCM can meter fuel. Technician B says a dirty MAF can cause hesitation and fuel-trim errors. Who is correct?

• a.Both A and B✓
• b.Neither A nor B
• c.Technician B only
• d.Technician A only

The MAF sensor measures intake air mass so the PCM meters the correct fuel quantity, and a dirty or faulty MAF causes incorrect fueling, hesitation, and trim errors. Both technicians are correct. Diagnosis includes cleaning or replacing it and checking for unmetered air leaks.

A P0420 code (catalyst efficiency below threshold) most often indicates:

• a.A slipping transmission
• b.A faulty ABS sensor
• c.A degraded catalytic converter or an O2 sensor issue✓
• d.A worn wheel bearing

P0420 sets when the downstream O2 sensor signal mirrors the upstream too closely, suggesting the converter is no longer storing oxygen effectively. Causes include a worn converter, exhaust leaks, or faulty sensors. Underlying misfires or rich running can damage the converter and must be addressed first.

In a modern coil-on-plug ignition system, each coil:

• a.Stores fuel for injection
• b.Is triggered by a mechanical distributor
• c.Fires the spark plug directly on its cylinder, controlled by the PCM✓
• d.Powers all cylinders at once

Coil-on-plug systems place an individual coil at each spark plug, fired by the PCM through the ignition driver, eliminating plug wires and the distributor. This improves spark control and misfire diagnosis. A failed coil typically causes a cylinder-specific misfire code.

A knock sensor allows the PCM to:

• a.Read vehicle speed
• b.Control the fuel pump
• c.Measure exhaust oxygen
• d.Detect detonation and retard ignition timing to protect the engine✓

The knock sensor detects the vibration of detonation so the PCM can retard timing and prevent engine damage. Persistent knock can come from low-octane fuel, carbon buildup, or overheating. A faulty sensor may cause reduced performance or a code.

The EVAP system is designed to:

• a.Increase fuel pressure
• b.Cool the intake charge
• c.Filter engine oil
• d.Capture and burn fuel vapors from the tank rather than venting them✓

The evaporative emission system stores fuel vapors in a charcoal canister and later purges them into the intake to be burned, preventing release to the atmosphere. A loose or faulty gas cap is a common cause of small-leak codes. It is tested for leaks during OBD-II monitors.

A loose or missing fuel cap most commonly sets which type of code?

• a.A coolant temperature code
• b.An ABS code
• c.An EVAP system leak code (such as P0455 or P0457)✓
• d.A misfire code

A poorly sealing fuel cap lets vapors escape and triggers an EVAP leak code, often the first thing to check for such faults. Tightening or replacing the cap and clearing the code frequently resolves it. Smoke testing finds larger leaks in the system.

Technician A says low fuel pressure can cause a lean misfire and hesitation. Technician B says a clogged fuel filter or weak pump can lower fuel pressure. Who is correct?

• a.Both A and B✓
• b.Technician A only
• c.Neither A nor B
• d.Technician B only

Insufficient fuel pressure leans the mixture, causing misfire, hesitation, and lack of power, and a restricted filter or failing pump is a common cause. Both technicians are correct. A fuel-pressure test and volume check confirm delivery problems.

The throttle position sensor (TPS) informs the PCM about:

• a.Battery voltage
• b.Coolant level
• c.Exhaust temperature
• d.Throttle plate angle (driver demand)✓

The TPS reports how far the throttle is open so the PCM can adjust fuel, timing, and transmission strategy. A faulty or dead-spot TPS causes hesitation, surging, or erratic shifts. Its signal is checked with a scan tool or by watching voltage sweep.

A vehicle fails an emissions test for high hydrocarbons (HC). This is most commonly associated with:

• a.A worn wheel bearing
• b.Excessive coolant
• c.Low tire pressure
• d.Unburned fuel from misfire, ignition, or rich-condition problems✓

High HC indicates unburned fuel escaping into the exhaust, typically from misfires, ignition faults, or an overly rich mixture. Diagnosing the misfire or fuel-control fault reduces HC. A failing catalytic converter can also raise tailpipe HC.

The PCM uses the crankshaft position sensor primarily to:

• a.Measure intake air temperature
• b.Detect wheel slip
• c.Read exhaust oxygen
• d.Determine engine speed and piston position for ignition and fuel timing✓

The crankshaft position sensor tells the PCM engine rpm and crank position so it can time spark and injection. Loss of this signal usually prevents the engine from starting. A cam/crank correlation code indicates timing has slipped between the two.

On an OBD-II vehicle, the data link connector (DLC) used to retrieve codes is standardized as a:

• a.9-pin round plug under the hood
• b.4-pin trailer connector
• c.16-pin connector, usually under the dash✓
• d.2-pin connector at the battery

OBD-II mandates a standardized 16-pin DLC, typically located under the driver's side dash, for scan-tool access. This standard allows generic tools to read codes and data across manufacturers. Certain pins carry power, ground, and communication signals.

The exhaust gas recirculation (EGR) system reduces which emission by lowering combustion temperature?

• a.Oxides of nitrogen (NOx)✓
• b.Carbon monoxide (CO)
• c.Carbon dioxide (CO2)
• d.Hydrocarbons (HC)

EGR routes inert exhaust gas back into the intake to lower peak combustion temperature, reducing the formation of NOx. A clogged EGR passage can cause knock and high NOx, while a stuck-open valve causes rough idle. Its operation is monitored by OBD-II.

A no-start with no spark and no injector pulse, but a good battery and cranking, most likely points to:

• a.A worn water pump
• b.A leaking A/C condenser
• c.A failed crankshaft position sensor or PCM/power issue✓
• d.A clogged cabin filter

When both spark and injector pulse are absent during cranking, a shared input such as the crankshaft position sensor or a PCM power/ground problem is a prime suspect. Scan-tool rpm during cranking helps confirm the crank signal. Systematic checks of power, ground, and reference sensors isolate the cause.

An outside micrometer is used to measure:

• a.Coolant temperature
• b.Precise outside dimensions such as shaft or rotor thickness✓
• c.Electrical resistance
• d.Torque on a fastener

An outside micrometer measures external dimensions to a thousandth of an inch or finer, such as a rotor or crankshaft journal. The reading combines the sleeve and thimble scales. Proper technique and calibration are essential for accuracy.

A torque wrench is used to:

• a.Measure bore diameter
• b.Tighten fasteners to a specified value✓
• c.Check tire tread depth
• d.Test battery voltage

A torque wrench applies a controlled, specified amount of tightening force so fasteners are neither loose nor overtightened. Proper torque is critical for head bolts, wheels, and many other parts. The wrench should be set back to its lowest setting when stored to preserve calibration.

Technician A says wheel lug nuts can be tightened in any order. Technician B says they should be tightened in a crisscross (star) pattern to the specified torque. Who is correct?

• a.Both A and B
• b.Neither A nor B
• c.Technician B only✓
• d.Technician A only

Lug nuts must be tightened gradually in a crisscross pattern to seat the wheel evenly and prevent rotor distortion. Uneven or over-tightening can warp rotors and damage studs. Technician A is incorrect.

Technician A says a vehicle should be supported at the manufacturer's designated lift points. Technician B says rated jack stands should support a vehicle before working underneath it. Who is correct?

• a.Both A and B✓
• b.Technician A only
• c.Technician B only
• d.Neither A nor B

Vehicles must be supported at designated lift points and secured on rated jack stands, never held only by a hydraulic jack. Both technicians are correct. Following these practices prevents damage and serious injury.

Technician A says a dial indicator measures runout, endplay, and gear backlash. Technician B says it must be set up perpendicular to the surface for an accurate reading. Who is correct?

• a.Both A and B✓
• b.Neither A nor B
• c.Technician B only
• d.Technician A only

A dial indicator measures small linear movements such as rotor runout, crankshaft endplay, and backlash, and the plunger must contact the surface perpendicularly for accuracy. Both technicians are correct. It reads deflection in thousandths of an inch.

A vehicle's service information (repair manual) is the best source for:

• a.Fuel prices
• b.Torque specifications, procedures, and wiring diagrams✓
• c.The owner's phone number
• d.Weather forecasts

Service information provides the manufacturer's specifications, step-by-step procedures, wiring diagrams, and fluid capacities needed for correct repairs. Using accurate data prevents mistakes and comebacks. Technicians should verify specs rather than rely on memory.

If a bolt must be torqued to 90 foot-pounds and the specification then calls for an additional 90-degree turn, this method is known as:

• a.Static balancing
• b.Preloading only
• c.Cross-torquing
• d.Torque-to-yield (torque-plus-angle)✓

Torque-plus-angle (torque-to-yield) tightens the fastener to a base torque and then a specified angle, stretching it for consistent clamp load. It is common on head bolts and other critical fasteners. A torque-angle gauge or electronic tool measures the additional rotation.

Proper personal protective equipment when grinding or working with the battery includes:

• a.Only gloves
• b.Only a hat
• c.Eye protection and appropriate gloves✓
• d.No protection needed

Eye protection guards against flying particles and battery acid, and gloves protect the hands from sharp edges and corrosive chemicals. Battery work also warrants care because of explosive hydrogen gas and acid. Safety equipment reduces the risk of injury.

Converting a measurement, a technician knows there are 25.4 millimeters in one inch. A 2-inch dimension equals approximately:

• a.50.8 mm✓
• b.254 mm
• c.12.7 mm
• d.2.54 mm

Multiplying 2 inches by 25.4 mm/inch gives 50.8 millimeters. Being comfortable converting between metric and standard units is important because vehicles use both. Measuring tools and specifications may be given in either system.

A feeler gauge is used to measure:

• a.The gap or clearance between two parts✓
• b.Tire pressure
• c.Electrical current
• d.Engine vacuum

A feeler gauge consists of thin metal blades of known thickness used to measure small gaps, such as valve lash or spark plug gap. The correct blade slides through the gap with a slight drag. It is a simple but precise clearance-measuring tool.

A valve spring is checked for squareness and free length. A spring shorter than spec or leaning against a square should be:

• a.Reinstalled as-is because free length rarely affects performance
• b.Replaced, because it has lost tension and may allow valve float✓
• c.Restored by heating the spring and re-tempering the metal
• d.Corrected by installing a thicker retainer and keeper set

A spring that has lost free length or is no longer square has weakened and can allow valve float at high rpm, so it must be replaced. Weak springs cause power loss and can let valves bounce off their seats. Both free length and load-at-height are compared to specification.

Blue smoke on startup that clears after a few seconds, with good compression, most often points to:

• a.A stuck-open thermostat that keeps the engine running cold
• b.A leaking fuel injector that floods the cylinder with fuel
• c.A cracked cylinder block allowing coolant into a cylinder
• d.Worn valve stem seals or valve guides letting oil seep in✓

Oil that seeps past worn valve guide seals while the engine sits gets burned at startup, producing brief blue smoke that clears as the guides drain. Compression stays normal because the rings are still sealing. Replacing the valve stem seals usually corrects it.

During a compression test, a low cylinder rises noticeably after squirting oil into it. This indicates the cause is:

• a.A burned or leaking valve that oil cannot seal at all
• b.A cracked piston crown venting compression to the crankcase
• c.A blown head gasket letting pressure escape to coolant
• d.Worn piston rings or cylinder walls that oil temporarily seals✓

Oil temporarily seals worn rings, so a reading that jumps up on the wet test points to ring or cylinder wear rather than a valve. If the reading stays low wet, the leak is at a valve or head gasket. This wet/dry comparison localizes the cause before teardown.

During a cylinder leak-down test, air escapes from the radiator or coolant reservoir. This indicates a leak at the:

• a.Exhaust valve, heard as air hissing from the tailpipe
• b.Head gasket or a cracked head or block✓
• c.Piston rings, heard as air escaping from the oil filler
• d.Intake valve, heard as air hissing from the throttle body

Air heard bubbling in the cooling system during leak-down means combustion pressure is reaching a coolant passage, pointing to a failed head gasket or crack. Air from the intake indicates an intake valve, from the exhaust an exhaust valve, and from the oil filler indicates rings. Where the air escapes tells you where the leak is.

One cylinder is weak and a worn camshaft lobe is suspected. Lobe wear reduces that cylinder's power because it:

• a.Increases oil pressure delivered to that one cylinder head
• b.Raises the compression ratio far above the other cylinders
• c.Decreases valve lift and duration on that cylinder✓
• d.Advances the ignition timing only on the affected cylinder

A rounded-off cam lobe opens its valve less far and for less time, reducing airflow and power on that cylinder. Flat-tappet cams are especially prone to lobe wear. Measuring valve lift at the retainer or comparing lobes confirms it.

Technician A says a noisy hydraulic lifter can be caused by low oil pressure or aerated oil. Technician B says a collapsed lifter can hold a valve open and cause a misfire. Who is correct?

• a.Technician B only
• b.Technician A only
• c.Neither A nor B
• d.Both A and B✓

Hydraulic lifters rely on clean, pressurized oil, so low pressure or air makes them clatter, and a lifter that bleeds down can affect valve action and cause a misfire. Both technicians are correct. Clean oil at the correct level and pressure keeps lifters quiet.

When installing a cylinder head, the head bolts should be tightened:

• a.Only by feel with an impact gun rather than a torque wrench
• b.From one corner straight across to the opposite corner in a single pass
• c.To full final torque in random order to save time on the job
• d.Gradually in the specified sequence, usually center outward✓

Tightening in the manufacturer's sequence, typically working outward from the center in stages, distributes clamp load evenly and prevents warping the head or crushing the gasket. Skipping the sequence causes leaks. Many heads use a torque-plus-angle procedure with new bolts.

An engine overheats only at idle or in slow traffic but cools at highway speed. The MOST likely cause is:

• a.A stuck-closed thermostat that blocks flow at all engine speeds
• b.A worn timing chain that has retarded the engine's valve timing
• c.An inoperative cooling fan or fan clutch✓
• d.A collapsed lower radiator hose that starves the water pump

At speed, ram air cools the radiator, but at idle the electric fan or fan clutch must move the air; if it fails, the engine overheats when stopped. A stuck thermostat overheats at all speeds. Verifying fan operation is the first check for this pattern.

Coolant dripping from the weep hole under the water pump, with a bearing whine, indicates:

• a.A failing water pump seal and bearing✓
• b.A cracked overflow bottle slowly losing coolant onto the ground
• c.A bad radiator cap venting coolant into the overflow reservoir
• d.A leaking heater core dripping coolant inside the passenger cabin

The weep hole is designed to leak when the internal pump seal fails, protecting the bearing from coolant; leakage plus noise means the pump is worn out. Continued use risks pump seizure and belt or timing damage. Replacing the pump and inspecting the belt corrects it.

A serpentine belt that squeals on acceleration and shows a glazed underside most likely needs:

• a.A permanent coating of belt dressing to quiet the squealing noise
• b.A belt one size wider than specified to grip the pulleys better
• c.The tensioner removed entirely so the belt can run more freely
• d.A new belt plus inspection of the automatic tensioner✓

Glazing and squeal indicate belt wear or a weak tensioner that no longer maintains proper tension, so the belt should be replaced and the tensioner checked. A worn tensioner spring lets the belt slip. Belt dressing only masks the problem temporarily.

A 50/50 mix of antifreeze and water is used instead of straight antifreeze mainly because the mix provides:

• a.Extra lubrication for the water pump as its single main purpose
• b.A higher freezing point than a mixture that contains added water
• c.Better heat transfer with freeze and boil protection✓
• d.A lower material cost, which is the only reason it is specified

Water transfers heat better than pure antifreeze, so a balanced mix cools effectively while still protecting against freezing, boiling, and corrosion. Straight antifreeze actually transfers heat poorly and can raise operating temperature. The correct ratio and coolant type matter for protection.

All of the following can cause an engine to overheat EXCEPT:

• a.A thermostat stuck closed that will not let coolant circulate
• b.A low coolant level or an airlock trapped in the cooling system
• c.A radiator restricted or clogged with scale, debris, or bugs
• d.An overcharged air conditioning refrigerant system✓

Overheating comes from anything that blocks heat rejection or coolant flow, such as a stuck thermostat, low coolant, or a clogged radiator; an A/C overcharge does not directly overheat the engine coolant. Diagnosis follows coolant flow and airflow. The A/C system is a separate refrigerant circuit.

The bypass valve built into or around an oil filter is designed to:

• a.Drain oil out of the filter whenever the engine is shut off and cools
• b.Increase oil pressure permanently once the engine reaches operating speed
• c.Regulate engine coolant temperature by routing warm oil to the cooler
• d.Let oil bypass a clogged filter so parts still get oil✓

If the filter media becomes plugged, the bypass valve opens so unfiltered oil still reaches the bearings rather than starving them. Dirty oil is better than none for short-term protection. Regular oil changes prevent the filter from clogging in the first place.

In the oil rating 5W-30, the '5W' refers to the oil's:

• a.Detergent and dispersant strength rating measured under high heat
• b.Percentage of the total additive package blended into the base oil
• c.Cold-temperature (winter) flow characteristics✓
• d.Operating oil pressure the engine develops at its normal idle speed

In a multi-viscosity oil, the number before the W describes flow when cold for easier starting, while the second number describes viscosity at operating temperature. A lower W number flows better in the cold. Using the specified grade protects the engine across the temperature range.

Crankshaft endplay is measured with a dial indicator by prying the crank fore and aft. Excessive endplay indicates a worn:

• a.Main bearing whose vertical oil clearance has opened up with wear
• b.Thrust bearing✓
• c.Camshaft bearing that no longer supports the cam journals properly
• d.Connecting-rod bearing that has developed too much oil clearance

The thrust bearing controls the crankshaft's front-to-back movement, so excessive endplay points to thrust bearing wear. Too much endplay can cause a knock and disturb the crank sensor or converter. It is checked with a dial indicator against the crank snout.

A deep knock present at idle that worsens with load, following recent low oil pressure, most likely indicates:

• a.A slipping accessory drive belt riding on a worn or seized pulley
• b.A worn crankshaft bearing damaged by oil starvation✓
• c.A sticking EGR valve allowing exhaust to enter the intake at idle
• d.A loose spark plug that is not fully torqued into its cylinder head

Loss of oil film from low pressure damages the crankshaft bearings, producing a load-sensitive knock. A rod bearing knock is often quieted by disabling that cylinder, while a main bearing knock is a heavier, lower thump. Confirming oil pressure and inspecting bearings is required.

When installing piston rings, the ring end gaps should be:

• a.Aligned directly over the wrist pin so the gaps share a common axis
• b.Staggered around the piston, not aligned with each other✓
• c.Positioned all together on the thrust side of the piston skirt
• d.Butted tightly together with essentially zero end-gap clearance

Staggering the end gaps keeps combustion pressure from blowing straight down through aligned gaps, reducing blow-by and oil consumption. The correct end gap clearance is also checked in the bore with a feeler gauge. Aligned gaps cause smoking and pressure loss.

A light knocking or slapping noise loudest on a cold start that quiets as the engine warms most likely indicates:

• a.A leaking head gasket letting combustion gases into the cooling system
• b.A clogged catalytic converter creating exhaust restriction under load
• c.Piston slap from excessive piston-to-wall clearance✓
• d.A worn water pump bearing that only makes noise once fully warmed

Piston slap occurs when a worn piston rocks in the bore while cold, and it quiets as the piston expands with heat. It is usually not immediately harmful but indicates cylinder wear. A cracked piston skirt can produce a similar cold noise.

A ticking noise loudest when the engine is cold that diminishes as it warms, near the exhaust, often indicates:

• a.A slipping timing chain that has begun to jump teeth on the sprocket
• b.A cracked exhaust manifold or a leaking manifold gasket✓
• c.A worn crankshaft main bearing that knocks harder as clearance grows
• d.A failing oil pump that cannot maintain pressure at operating speed

A cracked manifold or leaking gasket ticks when cold because the gap is largest before the metal expands and closes it with heat. The sound is a rhythmic exhaust tick. Inspection and a leak test confirm the crack.

A vacuum gauge on the intake shows a steady but low reading (about 12 in-Hg) at idle. This most commonly indicates:

• a.A single burned valve, which would drop the needle rhythmically
• b.Excessive oil pressure being transmitted through the intake manifold
• c.Retarded ignition or valve timing, or a vacuum leak✓
• d.A perfectly healthy engine reading well within normal specification

A steady low vacuum reading points to late timing or a general leak rather than a single-cylinder fault, which would make the needle drop rhythmically. Vacuum testing is a quick way to gauge engine condition. Comparing the pattern to known signatures guides diagnosis.

A core (freeze) plug leaking coolant on the side of the block should be:

• a.Replaced with a new plug and sealer✓
• b.Ground off flush with the block and simply left open to the air
• c.Sealed temporarily with tape and left in service until it worsens
• d.Left alone if the leak appears small and slow at the moment

A corroded or pushed-out core plug leaks coolant and must be replaced, since it is a sealed opening left from casting. Coolant loss leads to overheating. The new plug is installed with sealer and driven in squarely.

On an interference engine, a broken timing belt will most likely cause:

• a.A sudden increase in oil pressure as the camshaft stops turning
• b.A slipping clutch as the engine loses power to the drivetrain
• c.Only a simple no-start condition with no other internal damage
• d.Valve-to-piston contact and internal engine damage✓

In an interference design the valves and pistons share the same space at different times, so a broken belt lets them collide, bending valves or worse. This is why timing belts have strict replacement intervals. A non-interference engine simply stops without contact.

Valve lash adjusted too tight (too little clearance) on a solid-lifter engine can cause:

• a.Increased oil consumption from oil pulled past the valve guides
• b.A burned valve from being held slightly off its seat✓
• c.Higher oil pressure because the lifters bleed down more slowly
• d.Excessive valvetrain noise as the rocker hammers the valve tip

Too little clearance can hold a valve off its seat as the engine heats and parts expand, preventing the valve from cooling through the seat and burning it. Too much lash instead causes noise. Correct lash allows full seating and heat transfer.

Cylinder head flatness (warp) is checked with a:

• a.Compression tester threaded into each spark plug hole in turn
• b.Vacuum gauge connected to a port on the intake manifold runner
• c.Dial bore gauge set to the diameter of each cylinder in the block
• d.Straightedge and feeler gauge across the deck✓

A precision straightedge laid across the head with a feeler gauge slipped underneath reveals warp beyond the flatness limit. Excess warp requires resurfacing. This check is done in several directions across the deck.

With a rocker arm ratio of 1.6:1 and a cam lobe lift of 0.300 inch, the valve lift is approximately:

• a.1.600 inch, equal to the rocker arm ratio expressed in inches
• b.0.300 inch, the same as the measured lobe lift on the camshaft
• c.0.188 inch, found by dividing lobe lift by the rocker arm ratio
• d.0.480 inch✓

Rocker arm ratio multiplies lobe lift, so 0.300 inch times 1.6 equals 0.480 inch of valve lift. The rocker acts as a lever to increase lift at the valve. Understanding the ratio matters when comparing cam specs and valve movement.

A voltmeter with one lead in the coolant and one on the battery negative reads a high DC voltage. This indicates:

• a.A perfectly normal, healthy cooling system with fresh coolant inside
• b.Electrolysis that can corrode cooling-system metals✓
• c.A thermostat stuck closed and raising the engine's temperature
• d.A weak battery that simply needs recharging or replacement soon

Stray current through the coolant, often from a poor engine ground, creates electrolysis that eats away radiators, heater cores, and pump parts. Fresh coolant with intact inhibitors and good grounds keep it low. A high reading calls for finding the ground fault.

A chemical block tester (combustion leak test) checks for a head gasket leak by detecting combustion gases in the:

• a.Coolant, shown by a color change in the test fluid✓
• b.Intake manifold, measured as a change in idle vacuum reading
• c.Exhaust stream, measured as a rise in tailpipe backpressure
• d.Engine oil, measured by comparing hot and cold oil viscosity

The block tester draws air from the coolant reservoir through a blue fluid that turns yellow if combustion gases are present, confirming a head gasket or crack. It detects hydrocarbons that should never reach the coolant. It is a quick, non-invasive test.

Detonation (spark knock) differs from pre-ignition in that detonation is:

• a.A condition caused only by an excessively rich air-fuel mixture
• b.Uncontrolled combustion after the spark collides with the flame✓
• c.Combustion that begins before the spark plug fires from a hot spot
• d.A completely normal combustion event that occurs at every idle

Detonation is a secondary autoignition after the plug fires, whose pressure spikes collide with the normal flame and cause the knock, while pre-ignition ignites before the spark from a hot spot. Both can damage pistons. Low octane, carbon, lean mixtures, and overheating promote knock.

Thick, dark sludge found throughout an engine is most commonly the result of:

• a.Frequent long highway trips that keep the oil fully warmed up
• b.Neglected oil changes and extended drain intervals✓
• c.Installing a fresh oil filter at every scheduled service interval
• d.Using a full-synthetic oil that resists breaking down under heat

Sludge forms when oil oxidizes and collects contaminants because it was not changed on schedule, clogging passages and starving parts. Short trips and skipped services accelerate it. Regular changes with the correct oil prevent sludge.

The oil pressure relief valve in the lubrication system:

• a.Cools the oil by routing it through a heat exchanger in the pan
• b.Limits peak oil pressure by returning excess oil to the pan✓
• c.Increases oil pressure without limit as engine speed keeps rising
• d.Filters contaminants out of the oil before it reaches the bearings

The relief valve opens when pressure exceeds a set point, bleeding oil back to the sump so the system is not over-pressurized. A stuck valve can cause abnormally high or low pressure. It protects seals, the filter, and galleries.

A hiss that changes with throttle, plus a rough idle and lean fuel trims, most likely indicates:

• a.A vacuum or intake manifold gasket leak adding unmetered air✓
• b.A worn crankshaft bearing that knocks louder as engine load rises
• c.A slipping serpentine belt squealing under accessory drive load
• d.A clogged oil filter forcing oil through the filter's bypass valve

Unmetered air entering through a leaking intake or vacuum line makes a hiss and leans the mixture, roughening idle and driving fuel trims positive. Smoke testing pinpoints the leak. Sealing the leak restores idle quality.

The purpose of the crankcase ventilation (PCV) system in managing airflow is to prevent:

• a.Pressure buildup and sludge from blow-by in the crankcase✓
• b.Engine coolant from being drawn into the oil through the galleries
• c.The catalytic converter from overheating during hard acceleration
• d.The alternator from overcharging the battery at higher rpm

By drawing blow-by vapors out of the crankcase, the PCV system relieves internal pressure and reduces moisture and sludge, sending the vapors to be burned. A blocked system builds pressure that pushes out oil at seals. It also lowers emissions.

After a coolant refill, an engine has intermittent overheating and inconsistent heater output. The MOST likely cause is:

• a.A cracked cylinder head letting combustion gases into the coolant
• b.A worn oil pump unable to maintain pressure at operating speed
• c.A seized brake caliper dragging and overheating one front wheel
• d.Trapped air (an airlock) that must be bled from the system✓

Air trapped after service blocks coolant flow, causing erratic temperature and poor heat until it is purged through the bleeder or by proper fill procedure. Many engines require a specific bleeding sequence. Confirming full coolant flow resolves it.

Technician A says a straightedge check can reveal a warped intake manifold sealing surface. Technician B says an intake gasket leak can cause coolant loss or a vacuum leak. Who is correct?

• a.Technician A only
• b.Neither A nor B
• c.Both A and B✓
• d.Technician B only

A straightedge reveals a warped intake flange, and depending on design an intake gasket can leak coolant, oil, or vacuum. Both technicians are correct. The failure mode depends on which passages the gasket seals on that engine.

Technician A says excessive valve guide clearance can cause oil consumption and smoke. Technician B says worn guides can cause erratic seating and a misfire. Who is correct?

• a.Technician B only
• b.Neither A nor B
• c.Both A and B✓
• d.Technician A only

Loose guides let oil down the stems and allow the valve to wander off its seat, causing oil burning and possible misfire. Both technicians are correct. Guide and seal service restores control of the valve and oil.

A shudder at light throttle around 40-50 mph that smooths out under harder acceleration most likely indicates:

• a.An unbalanced tire producing a vibration only at highway speed
• b.A worn outer CV joint that clicks and shudders during tight turns
• c.A torque converter clutch (lockup) shudder✓
• d.A slipping serpentine belt losing grip on the accessory pulleys

TCC shudder appears when the converter clutch applies at cruise, often from worn friction material or degraded fluid, and it disappears when the clutch releases under heavier throttle. Fresh fluid of the correct type sometimes cures early shudder. Scan data confirms lockup timing.

In a modern electronically controlled automatic, shift points are determined mainly by the:

• a.Mechanical governor and vacuum modulator working entirely on their own
• b.Throttle cable position acting alone with no electronic input at all
• c.A driver-adjustable vacuum valve mounted on the intake manifold
• d.Control module using sensor inputs and shift solenoids✓

Electronic automatics use the control module reading throttle, speed, and load to command shift solenoids, replacing the old governor and vacuum modulator. This allows adaptive, precise shifting. Faults set codes read with a scan tool.

The valve body in an automatic transmission functions to:

• a.Generate the engine's intake vacuum used by the accessory systems
• b.Direct hydraulic fluid to apply the correct clutches and bands✓
• c.Charge the battery through a gear-driven generator inside the case
• d.Cool the engine oil by passing it through internal fluid passages

The valve body is the hydraulic control center that routes pressurized fluid to the apply devices for each gear, guided by the solenoids and pump pressure. A stuck valve causes shift complaints. It works with the electronic controls to time shifts.

Planetary gearsets are used in automatic transmissions mainly because they can provide:

• a.Several gear ratios plus reverse in a compact, strong unit✓
• b.Electrical power generation to help run the vehicle's accessories
• c.Cooling for the engine by circulating fluid through the gearset
• d.Only one fixed ratio, which keeps the whole assembly very simple

By holding or driving different members, a planetary set delivers several forward ratios plus reverse in a compact package that stays in constant mesh. This makes automatic shifting smooth and durable. Clutches and bands control which members are held.

An automatic transmission will not move in any gear, forward or reverse. A likely cause is:

• a.A single worn synchronizer preventing engagement of just one gear
• b.A dragging brake caliper holding the vehicle back on one wheel
• c.A worn outer CV joint that has begun to click loudly during turns
• d.Very low fluid or a failed pump producing no line pressure✓

No movement in any range points to a loss of hydraulic pressure from low fluid or a failed pump, since pressure applies every gear. A pressure test confirms it. Synchronizers exist only in manual transmissions.

A manual transmission grinds only when shifting into one particular gear. The MOST likely cause is:

• a.A low engine oil level starving the transmission of lubrication
• b.A worn front wheel bearing that drones and roughens with speed
• c.A slipping serpentine belt losing grip under accessory drive load
• d.A worn synchronizer for that specific gear✓

A synchronizer matches shaft speeds so the gear engages smoothly; when one wears, that specific gear grinds while others shift fine. Clutch drag can also cause grinding but usually affects all gears. Replacing the worn synchro corrects it.

The synchronizer in a manual transmission functions to:

• a.Generate line pressure that applies the clutches during each shift
• b.Match gear and shaft speeds for smooth, clash-free engagement✓
• c.Engage the starter motor with the flywheel ring gear when cranking
• d.Lubricate the clutch disc so it engages the flywheel more smoothly

The synchronizer brings the rotating gear and shaft to the same speed before the collar locks them, preventing clash. Worn synchros cause grinding in that gear. Double-clutching can help engage a transmission with weak synchros.

A manual-transmission clutch that chatters (shudders) as it engages is most often caused by:

• a.An oil-soaked disc or a worn or warped component✓
• b.A stuck-closed engine thermostat causing the engine to run cold
• c.An overcharged air conditioning system raising the high-side pressure
• d.Too much brake fluid in the hydraulic clutch master cylinder

Chatter usually comes from a glazed or oil-soaked disc, a warped flywheel, or worn parts that grab unevenly during engagement. A leaking rear main or input seal can soak the disc. Correcting the leak and replacing the disc cures it.

A hydraulic clutch pedal that goes to the floor and will not disengage the clutch most likely has:

• a.A worn front wheel bearing that has developed play and roughness
• b.Low fluid or air in the clutch hydraulics, or a failed cylinder✓
• c.A warped brake rotor causing a pulsation through the brake pedal
• d.A clogged cabin air filter restricting airflow from the HVAC vents

Loss of hydraulic pressure from low fluid, air, or a leaking master or slave cylinder prevents the clutch from releasing, so the pedal feels dead. Bleeding and repairing the leak restores operation. The clutch hydraulic system is separate from the brakes but uses similar fluid.

A noise present only when the clutch pedal is depressed, stopping when released, most likely indicates a worn:

• a.Water pump bearing, which whines whenever the engine is running
• b.Release (throwout) bearing✓
• c.Pilot bearing, which instead is noisy with the transmission in gear
• d.Front wheel bearing, which drones and changes with vehicle speed

The release bearing spins only while the pedal is down and pressing on the pressure plate fingers, so noise that appears then points to it. A pilot bearing, by contrast, is noisy with the pedal down and the transmission in gear. Replacing the release bearing with the clutch is standard practice.

A flywheel with heat cracks or a worn friction surface should be:

• a.Left as-is as long as a brand-new clutch disc is being installed
• b.Painted over the cracked area to seal the heat checks in the metal
• c.Coated with high-temperature grease to smooth the worn surface
• d.Resurfaced or replaced during clutch service✓

A scored or heat-checked flywheel prevents proper clutch engagement and causes slipping or chatter, so it is machined or replaced when the clutch is done. Dual-mass flywheels are inspected for excessive play and usually replaced. A fresh surface ensures full disc contact.

A clunk heard shifting from Drive to Reverse or on throttle tip-in, with the transmission otherwise fine, often indicates:

• a.A clogged fuel filter restricting flow to the fuel injectors
• b.A broken or worn engine or transmission mount✓
• c.A worn oxygen sensor that has slowed its response in the exhaust
• d.A low brake fluid level in the master cylinder reservoir

A failed mount lets the powertrain shift on its supports, producing a clunk during gear and load changes. Inspecting the mounts for cracks and separation confirms it. Worn U-joints can cause a similar driveline clunk.

The transfer case in a four-wheel-drive vehicle is used to:

• a.Split engine power between the front and rear axles✓
• b.Filter the engine oil before it reaches the crankshaft main bearings
• c.Increase air conditioning system pressure during heavy cooling loads
• d.Charge the vehicle's battery through an internal gear-driven generator

The transfer case distributes torque to both axles and often provides a low range for extra reduction. Low fluid or worn chains and clutches cause noise or engagement problems. It is serviced with the specified fluid.

A limited-slip differential that chatters or shudders while turning slowly is often corrected by:

• a.Increasing the tire pressure well above the placard specification
• b.Adding the specified friction-modifier additive to the gear oil✓
• c.Replacing the wheel speed sensor mounted at the affected axle
• d.Adding a small amount of brake fluid directly into the axle housing

Clutch-type limited-slip units need a friction modifier so the plates release smoothly; without it, they grab and chatter in tight turns. Using the correct gear oil with additive cures it. Persistent noise may mean worn clutch plates.

When setting up a ring-and-pinion gear, the tooth contact pattern is checked to verify correct:

• a.Pinion depth and backlash✓
• b.Tire balance and radial runout across the drive wheels of the axle
• c.Brake fluid level within the master cylinder before the road test
• d.Ignition timing advance measured at the crankshaft position sensor

A marking-compound pattern on the ring gear teeth reveals whether pinion depth and backlash are correct before final assembly. An improper pattern causes whine and premature wear. Shims and adjusters are changed to center the pattern.

Gear oil leaking from an axle seal onto the brake can cause:

• a.A charging system fault that illuminates the battery warning lamp
• b.Contaminated linings and a brake pull or grab✓
• c.An evaporative emission leak code from the fuel vapor canister
• d.Higher engine oil pressure at idle and during cruising conditions

A leaking axle seal lets gear oil reach the brake shoes or pads, causing them to grab or the vehicle to pull. The seal must be replaced and the friction material cleaned or renewed. Ignoring it risks unsafe braking.

Many automatic transmissions route fluid through a cooler located in the:

• a.Air cleaner housing, where intake air blows across the fluid lines
• b.Fuel tank, where the cool fuel absorbs heat from the transmission
• c.Radiator, sometimes with a separate auxiliary cooler✓
• d.Exhaust manifold, using engine heat to warm the fluid when cold

ATF is cooled in a heat exchanger inside the radiator, sometimes with an added external cooler for heavy use, because heat is the main enemy of the fluid. A failed internal cooler can cross-contaminate coolant and ATF. Adequate cooling extends transmission life.

An automatic that shifts fine when cold but slips as it warms up most likely has:

• a.A clogged cabin air filter reducing airflow through the HVAC case
• b.A worn outer tie rod end introducing play into the steering
• c.A misadjusted parking brake dragging the rear brakes when warm
• d.Worn clutches or low pressure that worsen as fluid thins✓

As fluid warms and thins, marginal clutches or seals slip more, so a transmission that fails only when hot points to internal wear or low pressure. A pressure test at temperature helps confirm. Correct fluid level and condition are checked first.

A momentary rise in engine rpm during an upshift, with no matching increase in vehicle speed, is called:

• a.Engine braking felt when the driver lifts off the throttle downhill
• b.Shift flare (slippage during the shift)✓
• c.Converter lockup engaging the clutch to eliminate fluid slippage
• d.Torque multiplication produced by the converter during acceleration

Flare happens when the oncoming clutch or band applies too slowly and engine speed briefly runs up during the shift, indicating wear or low pressure. It stresses the friction elements. Diagnosis includes fluid condition, pressure, and solenoid operation.

A code for the torque converter clutch circuit (such as P0741) most often relates to:

• a.A worn front wheel bearing that drones and roughens with speed
• b.The TCC failing to lock up or slipping too much✓
• c.A leaking radiator cap venting coolant into the overflow bottle
• d.A faulty ABS wheel-speed sensor at one of the four wheels

This code sets when the module sees the converter clutch not achieving or holding lockup, from a stuck solenoid, worn clutch, or fluid issues. Persistent slip overheats the fluid. Checking the solenoid, fluid, and valve body is the next step.

A manual transmission that pops out of gear on its own most commonly indicates:

• a.Worn shift detents, synchronizers, or a broken mount✓
• b.A clogged fuel injector causing a lean misfire under acceleration
• c.A weak battery that cannot hold a full charge between road trips
• d.An overcharged air conditioning system raising the high-side pressure

Worn detent springs, damaged synchro teeth, or excessive powertrain movement from a bad mount let the gear disengage under load. Inspection of the linkage, internal parts, and mounts finds the cause. Continued use accelerates wear.

The correct way to remove air from a hydraulic clutch system is to:

• a.Bleed at the slave cylinder while keeping the reservoir full✓
• b.Pump the pedal until it firms up and then simply drive the vehicle
• c.Loosen the transmission mount to let the trapped air work its way out
• d.Add a heavier, thicker fluid so the trapped air cannot compress

Air makes the clutch hydraulic pedal soft and prevents full release, so the system is bled at the slave bleeder like a brake circuit while topping the reservoir. A gravity or pressure bleed removes trapped air. Then full disengagement returns.

A torn CV joint boot found during inspection should be addressed promptly because:

• a.It causes the alternator to overcharge and boil the battery dry
• b.It reduces engine oil pressure delivered to the crankshaft bearings
• c.It sets an evaporative emission leak code from the vapor canister
• d.Lost grease and entering dirt will quickly ruin the joint✓

Once the boot tears, grease flings out and grit gets in, wearing the joint until it clicks and fails. Replacing the boot early, before contamination, can save the joint. A neglected joint requires a full axle replacement.

A vehicle will not crank in Park but cranks in Neutral. The MOST likely cause is:

• a.A slipping torque converter that cannot transmit engine torque
• b.A leaking axle seal allowing gear oil to reach the brake linings
• c.A worn clutch disc slipping under load in the higher forward gears
• d.A faulty transmission range (neutral safety) switch✓

The range switch tells the starter circuit the vehicle is in Park or Neutral; when it is misadjusted or failing, starting may work in only one position. Adjusting or replacing the switch restores normal cranking. It also feeds gear position to the module.

A transmission fluid cooler line that leaks lowers the fluid level, which can lead to:

• a.Improved shift quality because less fluid means quicker apply
• b.A stronger clutch engagement as the fluid level slowly drops
• c.Higher fuel economy from reduced drag inside the transmission case
• d.Slipping, overheating, and internal damage✓

Low fluid from a leaking cooler line reduces pressure and cooling, causing slip and heat that damage the clutches. The line is repaired and the fluid refilled to the correct level. Prompt repair prevents costly failure.

An automatic transmission used for frequent trailer towing benefits most from:

• a.A higher-octane fuel to lower the transmission's operating temperature
• b.An auxiliary cooler to control fluid temperature✓
• c.A larger battery to supply the extra current the transmission draws
• d.A thicker grade of engine oil to reduce internal friction and heat

Towing loads the transmission and raises fluid temperature, so an auxiliary cooler keeps the ATF within a safe range and extends its life. Heat is the leading cause of transmission failure. Fluid condition should also be monitored under heavy use.

The vehicle speed sensor (VSS) signal is used by the transmission controller to:

• a.Control the air conditioning compressor clutch air gap and cycling
• b.Measure the oxygen content in the exhaust for fuel-trim correction
• c.Help determine shift timing and converter lockup✓
• d.Read the coolant level in the radiator and its overflow reservoir

The controller compares vehicle speed with throttle and load to schedule shifts and apply the converter clutch. A faulty VSS can cause erratic or no shifts and a speedometer fault. Its signal is verified with a scan tool.

In a continuously variable transmission (CVT), the ratio is changed by:

• a.Shifting between fixed planetary gearsets held by clutches and bands
• b.Varying the effective diameter of two belt-linked pulleys✓
• c.Engaging a series of dog clutches to select individual gear pairs
• d.Changing the final drive ring-and-pinion gear ratio on the fly

A CVT uses a steel belt or chain running between variable-width pulleys, so moving the pulley halves changes the ratio smoothly with no fixed steps. This keeps the engine near its most efficient speed. CVT fluid is a specific type not interchangeable with ATF.

Technician A says worn universal joints can cause a driveline clunk and vibration. Technician B says a bent or unbalanced driveshaft can cause a speed-related vibration. Who is correct?

• a.Both A and B✓
• b.Technician B only
• c.Neither A nor B
• d.Technician A only

Worn U-joints clunk and vibrate, and a bent or unbalanced shaft vibrates more as speed rises. Both technicians are correct. Inspecting the joints, runout, and balance isolates the source.

Technician A says overheated automatic transmission fluid turns dark and smells burnt. Technician B says burnt fluid indicates the friction material may be damaged. Who is correct?

• a.Neither A nor B
• b.Technician A only
• c.Technician B only
• d.Both A and B✓

Overheating darkens the fluid and produces a burnt odor, and that heat comes from slipping friction elements that are wearing. Both technicians are correct. Fluid condition is an important early diagnostic clue.

The hydraulic brake system transmits force to all wheels based on the principle that:

• a.Liquids expand in volume when they are put under high pressure
• b.Fluid pressure gradually decreases as it travels farther from the pedal
• c.Pressure on a confined fluid is transmitted equally throughout✓
• d.Fluid compresses under pressure and stores energy to release later

Pascal's principle states that pressure in a confined, incompressible fluid is transmitted undiminished throughout, which is why pedal force reaches every wheel. Air in the system defeats this because air compresses. This is the basis of hydraulic braking.

A modern tandem (dual) master cylinder is designed so that:

• a.Both hydraulic circuits fail together the moment one springs a leak
• b.A leak in one circuit still leaves the other working✓
• c.It boosts pedal effort by itself without any vacuum or hydraulic assist
• d.It also stores and supplies fluid for the vehicle's clutch system

The tandem master cylinder splits braking into two independent hydraulic circuits so that a single leak leaves partial braking rather than total loss. The pedal travels farther and the warning light comes on. This redundancy is a required safety feature.

The red brake warning light (not the ABS lamp) can be triggered by:

• a.Low fluid or a pressure difference between the two circuits✓
• b.A dirty cabin air filter that has restricted airflow from the vents
• c.A high engine coolant temperature approaching the overheat point
• d.A worn wheel-speed sensor sending an erratic signal to the module

The base brake warning lamp responds to low reservoir fluid, an applied parking brake, or a pressure imbalance sensed by the differential switch. It signals a hydraulic problem needing attention. The separate amber ABS lamp covers anti-lock faults.

Drum brakes use a self-adjuster mechanism that typically operates when the:

• a.Vehicle is parked and left on a steep hill with the brake applied
• b.Wheels are removed from the vehicle during a routine tire rotation
• c.Ignition switch is first turned on before the engine begins to crank
• d.Brakes are applied while the vehicle is backing up✓

Many drum self-adjusters take up shoe clearance during reverse stops, turning the star wheel a little at a time. If the mechanism seizes, the pedal gets low as the shoes wear. Proper adjustment restores a high, firm pedal.

A wheel cylinder leaking brake fluid onto the drum brake shoes will cause:

• a.An increase in fuel economy from lower rolling resistance at that wheel
• b.An overcharged battery from the extra draw on the charging system
• c.Contaminated linings and reduced or grabby braking there✓
• d.A high, firm pedal that requires very little effort to fully stop

A leaking wheel cylinder soaks the shoes with fluid, ruining the friction material and causing grab or reduced braking. Both the cylinder and shoes must be replaced. Fluid on the drum also signals the leak.

Brake fade after repeated hard stops, where the pedal stays firm but braking weakens, is most often:

• a.A cracked windshield distracting the driver during the hard stops
• b.Mechanical fade from overheated linings losing friction✓
• c.A worn front wheel bearing that has developed play and roughness
• d.Air being drawn into the master cylinder past its worn primary seal

When linings overheat they temporarily lose their friction coefficient, so the pedal feels normal but stopping power drops. Fluid fade, by contrast, gives a soft pedal from boiling fluid. Cooling and quality linings reduce mechanical fade.

After machining a brake rotor on a lathe, the technician should apply a:

• a.Bead of RTV silicone around the rotor edge to reduce vibration
• b.Non-directional finish and clean it before installing pads✓
• c.Layer of thread sealant to the rotor hat where it meets the hub
• d.Thin coat of high-temperature grease across the rotor friction surface

A non-directional finish helps the new pads seat and prevents pad noise or pull, and the surface is cleaned of metal dust before assembly. Directional swirl marks can act like a screw thread. Proper prep improves braking and reduces comebacks.

Excessive lateral runout of a brake rotor is measured with a:

• a.Test light probed across the wheel-speed sensor connector
• b.Vacuum gauge connected to a port on the power brake booster
• c.Feeler gauge inserted between the brake pad and the rotor surface
• d.Dial indicator reading against the rotor face✓

A dial indicator mounted to read the spinning rotor face shows lateral runout, which over time creates thickness variation and pedal pulsation. Excess runout may come from the rotor, hub, or debris behind the rotor. It is corrected by machining, indexing, or replacement.

A seized caliper slide pin will most likely cause:

• a.Uneven (tapered) pad wear and a possible pull✓
• b.An evaporative emission leak code from the fuel vapor canister
• c.A charging system fault that lights the battery warning lamp
• d.A boiling radiator and rapid loss of coolant from the overflow

When a slide pin sticks, the caliper cannot center over the rotor, so one pad wears faster and the vehicle may pull. Cleaning, lubricating, or replacing the pins and boots restores even movement. Neglected pins also cause drag and heat.

Compared with semi-metallic pads, ceramic brake pads are generally chosen for:

• a.Lower noise and less visible brake dust✓
• b.Higher rotor wear under every driving condition and temperature
• c.A lower purchase cost being their single and only real advantage
• d.The greatest possible heat capacity for sustained racing use only

Ceramic pads typically run quieter and produce lighter-colored, less-visible dust, which suits many passenger vehicles. Semi-metallic pads handle high heat well but can be noisier and dustier. Pad choice balances noise, dust, and heat needs.

A constant high-pitched squeal that stops when the brakes are applied usually indicates:

• a.The pad wear indicator dragging on the rotor✓
• b.Air trapped in the master cylinder past the worn primary piston seal
• c.A worn front wheel bearing that drones and changes with vehicle speed
• d.A leaking wheel cylinder soaking the rear drum brake shoes with fluid

The mechanical wear indicator drags on the rotor when the pads are thin, squealing until the brakes are pressed. It is a warning to replace the pads soon. Ignoring it leads to metal-to-metal grinding and rotor damage.

The check valve in a vacuum brake booster is designed to:

• a.Bleed atmospheric air into the booster to firm up the brake pedal
• b.Adjust the parking brake cable tension automatically as pads wear
• c.Hold vacuum in the booster so a reserve is available✓
• d.Regulate hydraulic brake fluid pressure sent out to the four calipers

The one-way check valve traps engine vacuum in the booster so the driver gets assisted stops even after the engine stops or during low-vacuum conditions. A faulty valve gives a hard pedal or loss of reserve. It is a simple but important part.

A hydro-boost power brake system gets its assist from:

• a.The power steering pump's hydraulic pressure✓
• b.Exhaust backpressure captured and stored to help apply the brakes
• c.The alternator's electrical output routed to a motor on the booster
• d.Engine intake manifold vacuum, the same source used by a diaphragm booster

Hydro-boost uses pressurized power steering fluid instead of vacuum to provide brake assist, common on diesels and heavy vehicles with little manifold vacuum. A steering or belt problem can affect braking assist. It stores a small hydraulic reserve for stops after shutdown.

The ABS hydraulic control unit prevents lockup by:

• a.Applying the parking brake automatically during a hard braking event
• b.Adding engine intake vacuum to each individual wheel brake circuit
• c.Increasing the master cylinder bore size to raise hydraulic pressure
• d.Cycling solenoid valves to modulate pressure at a wheel✓

The modulator's solenoid valves cycle to hold, release, and reapply pressure at a wheel that is about to lock, based on wheel-speed data. This keeps the wheels rolling for steering control. The pump restores pressure during release cycles.

A damaged or contaminated tone ring (reluctor) at one wheel will most likely cause:

• a.A parking brake that will not hold the vehicle on a moderate grade
• b.A boiling master cylinder that overflows the brake fluid reservoir
• c.An erratic wheel-speed signal and false ABS activation or a code✓
• d.A soft, spongy brake pedal from air trapped in the hydraulic system

A cracked, rusty, or debris-covered tone ring produces an irregular signal, which the ABS module may read as a wheel about to lock, causing false activation or a code. Inspecting and cleaning or replacing the ring corrects it. The sensor air gap is also checked.

Electronic stability control (ESC) and traction control generally operate by using:

• a.The air conditioning compressor to add drag at the wheel that is slipping
• b.The evaporator core temperature sensor to detect a loss of traction
• c.The ABS wheel-speed sensors and hydraulic modulator✓
• d.The alternator diodes to divert electrical load away from the drive wheels

ESC and traction control build on ABS hardware, using wheel-speed and yaw data to apply individual brakes and cut engine torque to keep the vehicle stable. A shared sensor fault can disable all three systems. They enhance, not replace, the base brakes.

Steel brake lines are joined and sealed using a:

• a.Soldered lap joint that bonds the two line ends permanently together
• b.Double flare or ISO flare rated for high pressure✓
• c.Simple compression sleeve and nut like those used on water supply lines
• d.Rubber grommet pushed into the fitting to seal against fluid leakage

Brake lines must use a double (or ISO) flare designed to hold high hydraulic pressure safely; ordinary compression fittings are not approved for brake lines. A single flare can crack and leak. The correct flare and fittings ensure a reliable seal.

Before installing a new or rebuilt master cylinder, the technician should:

• a.Pack the internal bore and pistons with wheel bearing grease first
• b.Place it in a freezer overnight to shrink the seals for installation
• c.Fill the reservoir with power steering fluid and cycle the pistons
• d.Bench bleed it to remove the trapped air✓

Bench bleeding purges air from the master cylinder on the bench so the brakes can be bled properly after installation. Skipping this step traps air and gives a low, spongy pedal. Only the specified brake fluid is used.

A deteriorated flexible brake hose with an internal flap can act like a one-way valve, causing:

• a.One brake to drag because pressure cannot fully release✓
• b.An evaporative emission leak code from the fuel vapor canister
• c.Both rear brakes to lock together during any moderate stop
• d.A charging system fault that illuminates the battery warning lamp

When a hose breaks down internally, a flap can let pressure through but block its return, so that caliper stays partly applied and drags. The wheel overheats and pulls. Replacing the hose restores normal release.

A pulsation felt in the brake pedal that occurs mainly with rear drum brakes is most often caused by:

• a.Air trapped in the master cylinder past its worn primary piston seal
• b.An out-of-round brake drum✓
• c.A dirty cabin air filter restricting airflow through the HVAC case
• d.A worn oxygen sensor that has slowed its response in the exhaust

An out-of-round drum changes the shoe-to-drum contact as it rotates, producing a pulsation. Measuring the drum diameter at several points reveals it. Machining within limits or replacing the drum corrects it.

When bleeding brakes, keeping the master cylinder reservoir topped off matters because:

• a.Running it dry lets air back into the system✓
• b.It keeps the battery charged during the bleeding procedure
• c.It automatically adjusts the parking brake cable as fluid is added
• d.It cools the engine by circulating brake fluid through the radiator

If the reservoir empties during bleeding, the master cylinder draws in air and you have to start over. Maintaining the level keeps the process moving forward. Using fresh, correct-spec fluid also matters.

Approved caliper grease is applied to the caliper slide pins to:

• a.Let the caliper move freely and prevent binding✓
• b.Seal the hydraulic circuit against leaks at the caliper piston bore
• c.Provide extra friction between the brake pad and the rotor surface
• d.Raise the brake fluid's boiling point during hard repeated braking

Proper lubricant on the slide pins lets the caliper float and clamp evenly, preventing drag and uneven pad wear. The grease must be compatible with the rubber boots. Never put lubricant on the friction surfaces.

A vehicle pulls to one side during braking. All of the following can cause this EXCEPT:

• a.A restricted brake hose on one side limiting release at that wheel
• b.Contaminated linings on one wheel that grab or slip unevenly
• c.A seized caliper on one side that keeps its pads partly applied
• d.A pad set worn evenly the same amount on both front wheels✓

A brake pull comes from unequal braking side to side, such as a seized caliper, a restricted hose, or contaminated linings; pads worn evenly on both sides brake equally and do not pull. Diagnosis compares the two sides. Correcting the uneven condition centers the braking.

Brake linings that have become glazed (hard and shiny) from overheating will typically cause:

• a.A slow coolant leak from the engine's cooling system passages
• b.Reduced braking and noise until the linings are renewed✓
• c.A spongy, low pedal caused by air in the hydraulic brake lines
• d.An overcharged battery from extra load on the charging system

Glazing hardens the friction surface so it grips less and may squeal, lowering braking performance. Light glazing can sometimes be sanded, but badly glazed linings are replaced. Correcting the cause of overheating, such as a dragging caliper, prevents recurrence.

When the ABS warning lamp is on but the red brake lamp is off, the vehicle usually has:

• a.A parking brake that has locked and will not release the rear wheels
• b.No braking capability at all until the fault has been fully repaired
• c.A boiling master cylinder overflowing fluid from the reservoir cap
• d.Normal base braking with anti-lock disabled✓

An ABS-only fault disables anti-lock control but leaves conventional hydraulic braking working, so the pedal still stops the vehicle. The red lamp would indicate a base hydraulic problem instead. The ABS fault is diagnosed with a scan tool.

A banjo bolt connecting a brake hose to a caliper should be reassembled with:

• a.No sealing washers at all as long as the bolt is tightened firmly
• b.New copper crush washers, torqued to spec✓
• c.A coat of anti-seize applied to both of the washer sealing faces
• d.The original washers reused along with thread sealant on the bolt

Banjo fittings seal with soft copper crush washers that deform once, so new washers and proper torque are needed to prevent a leak. Reused washers often weep fluid. The banjo bolt has hollow passages for fluid flow.

The dry boiling point of a brake fluid is higher than its wet boiling point because:

• a.Absorbed moisture over time lowers the boiling point✓
• b.Pressure inside the sealed brake system has no effect on boiling
• c.The fluid gains fresh additives and improves as it ages in service
• d.Cold outdoor weather raises the fluid's boiling point substantially

Glycol brake fluid absorbs moisture in service, and that water lowers the boiling point, which is why the wet rating is lower than the fresh dry rating. Boiled fluid produces vapor and a spongy pedal. Periodic fluid replacement restores the margin.

Brake rotor thickness variation (parallelism) differs from lateral runout in that thickness variation is measured with a:

• a.Vacuum gauge connected to a port on the vacuum brake booster
• b.Micrometer at several points around the rotor✓
• c.Feeler gauge slipped between the brake pad and rotor at each wheel
• d.Dial indicator reading against the flat face of the spinning rotor

Thickness variation is the difference in rotor thickness measured with a micrometer at points around the disc, while runout is side-to-side wobble read with a dial indicator. Both cause pedal pulsation but are checked differently. Excess of either is corrected by machining or replacement.

A low brake pedal after a drum brake service, with no leaks or air, most often means the:

• a.Shoes need adjustment to reduce excess clearance✓
• b.Rotors have been machined thicker than the original specification
• c.Booster vacuum supply is much higher than the engine can produce
• d.Master cylinder bore is far too large for the vehicle's brake system

Freshly installed shoes with too much clearance require several pedal strokes or manual adjustment to take up, causing a low pedal until adjusted. The self-adjusters or a manual adjustment set the clearance. A properly adjusted drum brake gives a high pedal.

A firm pedal that requires very high effort, with the engine running, most likely indicates a problem with the:

• a.Parking brake cable that has stretched and gone out of adjustment
• b.Wheel-speed sensor sending an erratic signal to the ABS control module
• c.Vacuum booster or its vacuum supply✓
• d.ABS tone ring that has cracked or become coated with road debris

A failed booster, leaking check valve, or lost vacuum supply removes the assist, leaving a hard, high-effort pedal even though the hydraulics are fine. Checking vacuum at the booster and the check valve isolates it. The brakes still work but require much more force.

The residual pressure (check) valve sometimes used in drum brake circuits is designed to:

• a.Raise rear brake pressure only during an anti-lock braking event
• b.Store extra brake fluid to also supply the hydraulic clutch system
• c.Block the parking brake from applying while the vehicle is moving
• d.Keep slight line pressure so wheel cylinder cups stay seated✓

A small residual pressure keeps the wheel cylinder cup lips seated so air is not drawn in and response stays quick. It is used on drum circuits, not on disc circuits, which need full release. The proportioning or metering functions are separate.

Grease or brake fluid contamination on one set of brake linings typically causes:

• a.A charging system fault that turns on the battery warning lamp
• b.A pull or grab toward that wheel✓
• c.A perfectly balanced, straight stop with no change in braking feel
• d.A slow coolant leak from the engine's cooling system passages

Contaminated friction material changes that wheel's braking, causing the vehicle to grab or pull to one side. The source of contamination, such as a leaking seal or caliper, must be fixed and the linings replaced. Cleaning alone rarely restores the friction material.

During pressure or gravity brake bleeding, the goal is to:

• a.Purge air from the lines so the pedal is firm✓
• b.Adjust the wheel bearing preload at each corner of the vehicle
• c.Raise the boiling point of the brake fluid already in the system
• d.Add a small amount of air to soften the pedal for easier modulation

All bleeding methods remove compressible air so the pedal becomes firm and braking is consistent. Pressure, vacuum, gravity, and manual methods all achieve this. Some ABS units require a scan tool to cycle the modulator during bleeding.

Technician A says a seized caliper can cause a pull and a burning smell from overheating. Technician B says it can boil the brake fluid and cause a fade. Who is correct?

• a.Neither A nor B
• b.Technician A only
• c.Technician B only
• d.Both A and B✓

A stuck caliper drags, overheating that wheel, which causes a pull, odor, and can boil the fluid into vapor. Both technicians are correct. The caliper, slides, and hose are inspected to find the cause.

Technician A says ignored worn brake pads can score the rotor. Technician B says continued metal-to-metal braking reduces stopping power. Who is correct?

• a.Technician B only
• b.Neither A nor B
• c.Both A and B✓
• d.Technician A only

When the friction material is gone, the metal backing grooves the rotor and braking suffers. Both technicians are correct. Timely pad replacement avoids rotor damage and a longer stop.

Steering axis inclination (SAI) is the:

• a.Difference in the toe setting between the left and right front wheels
• b.Inward or outward tilt of the tire tread across its rolling surface
• c.Forward or rearward tilt of the steering axis, viewed from the side
• d.Inward tilt of the steering axis, viewed from the front✓

SAI is the inward tilt of the line through the steering pivots, viewed from the front, and it aids steering return and reduces required effort. It is built into the design and not directly adjustable. A bent part changes SAI and the included angle.

Setback in a wheel alignment refers to:

• a.The rear axle assembly being shifted ahead of the vehicle center
• b.The inward or outward tilt of the wheel measured from true vertical
• c.One front wheel sitting rearward of the other front wheel✓
• d.The measured distance between the two front tie rod adjusting sleeves

Setback describes one wheel sitting farther back than the opposite wheel, often from a collision or worn part. It can cause a pull or steering problems. It is compared side to side during a four-wheel alignment.

A vehicle that tracks slightly sideways (dog-tracks) usually has an incorrect:

• a.Front wheel camber angle set too far to the positive on both sides
• b.Thrust angle from rear axle position or rear toe✓
• c.Brake fluid level in the master cylinder reservoir sitting too low
• d.Battery voltage that drops when the steering is turned to full lock

The thrust angle is the direction the rear axle points; when it is off, the rear steers the vehicle at an angle and the steering wheel sits crooked. A four-wheel alignment corrects rear toe to center the thrust line. Bent parts or a shifted axle cause it.

In a MacPherson strut front suspension, the strut assembly serves as a damper and also as:

• a.The lower control arm that carries the vehicle's weight at each wheel
• b.The stabilizer bar that resists body roll during hard cornering
• c.An upper suspension locating member for the knuckle✓
• d.The steering gear that converts wheel input into road-wheel movement

The MacPherson strut combines the shock absorber with a structural role, locating the top of the knuckle so a separate upper control arm is not needed. This saves space and weight. The upper strut mount often includes a bearing for steering.

A binding or clunk felt through the steering when turning, traced to the top of a strut, often means a worn:

• a.Wheel-speed sensor sending an erratic signal to the ABS module
• b.Tie rod boot that has torn and let grease escape from the joint
• c.Upper strut mount or its bearing✓
• d.Brake caliper slide pin that has seized in its mounting bracket

The strut mount bearing lets the strut rotate with the steering; when it wears, turning produces a bind, clunk, or memory steer. Replacing the mount and bearing restores smooth steering. It is inspected during strut service.

A broken coil spring will most commonly cause:

• a.A high, hard brake pedal that requires extra effort to fully stop
• b.An evaporative emission leak code from the fuel vapor canister
• c.A charging system fault that turns on the battery warning lamp
• d.A sagging corner, noise over bumps, and possible tire contact✓

A broken coil lowers ride height at that corner and can rattle or let the tire rub, upsetting alignment and handling. The spring must be replaced, often in pairs for balance. Corrosion is a common cause of spring breakage.

Worn control arm bushings can cause:

• a.A stuck-closed thermostat that raises the coolant temperature
• b.Higher engine oil pressure at idle and during highway cruising
• c.Clunks, alignment changes, and tire wear✓
• d.An overcharged battery from extra draw on the charging system

Deteriorated bushings let the control arm shift, producing noise, altering caster and camber, and wearing tires. They are inspected for cracking and looseness. Replacement restores correct geometry and quiet operation.

In a parallelogram (recirculating-ball) steering linkage, the idler arm functions to:

• a.Support and pivot the outer end of the center link✓
• b.Generate the hydraulic pressure used to assist the driver's steering
• c.Adjust vehicle ride height as the load in the vehicle changes
• d.Sense wheel speed and report it to the anti-lock brake controller

The idler arm mirrors the pitman arm to keep the center link level and support the linkage on the passenger side. A worn idler arm causes play, wander, and tire wear. It is checked for vertical movement during inspection.

A recirculating-ball steering gear with excessive play on-center may be corrected by:

• a.Adjusting the sector (lash) screw to spec, if not worn out✓
• b.Adding brake fluid directly into the steering gear housing reservoir
• c.Replacing the wheel-speed sensors mounted at each front wheel
• d.Raising the tire pressure well above the placard specification

The sector adjustment removes excess lash in the gear's center position, restoring a tighter feel if the gear is not internally worn. Over-tightening causes binding. A badly worn gearbox is replaced instead.

A torn rack-and-pinion bellows (boot) should be replaced promptly because it:

• a.Sets an evaporative emission leak code from the fuel vapor canister
• b.Reduces the engine's oil pressure delivered to the crankshaft bearings
• c.Overcharges the battery by increasing load on the charging system
• d.Lets dirt and moisture into the rack, causing wear or leaks✓

The bellows keeps contaminants out of the inner tie rod and rack; once torn, grit and water enter and cause wear or a fluid leak. Replacing the boot early protects the rack. A neglected boot leads to costly rack replacement.

A power steering pump whine loudest at full lock, with a low fluid level, most likely means:

• a.A failed oxygen sensor that has slowed its response in the exhaust
• b.A clogged engine fuel filter restricting flow to the injectors
• c.A worn brake rotor causing a pulsation felt through the pedal
• d.Air in the system or low fluid, which is corrected first✓

Low fluid or aeration makes the pump whine, especially under the high load of full lock. Topping off the correct fluid and bleeding out the air often quiets it. A persistent noise after that may mean a worn pump.

On a vehicle with electric power steering (EPS), a loss of assist with a warning light usually means:

• a.The brake hydraulic system has air trapped in one of its circuits
• b.The air conditioning system has been overcharged with refrigerant
• c.The EPS system set a fault and disabled assist, leaving manual steering✓
• d.The engine is completely out of oil and has lost oil pressure

An EPS fault disables the motor assist but the steering remains mechanically connected, so the wheel gets heavy and a light comes on. The system is diagnosed with a scan tool for codes. Common causes include the torque sensor, motor, or a voltage problem.

Excessive free play felt at the steering wheel before the wheels respond can be caused by:

• a.An overcharged air conditioning system raising the high-side pressure
• b.Worn tie rod ends, idler arm, or a loose steering gear✓
• c.A weak battery unable to hold a charge between vehicle uses
• d.A dirty cabin air filter restricting airflow through the HVAC case

Play in the linkage or gear shows up as steering-wheel free travel before the wheels turn, causing wander and imprecise steering. Each joint is checked for looseness. Worn parts are replaced before an alignment.

A wheel bearing drone that changes as the vehicle is gently swayed side to side is diagnosed as:

• a.A worn wheel bearing on the loaded side✓
• b.A worn oxygen sensor that has slowed its response in the exhaust
• c.A leaking heater core dripping coolant inside the passenger cabin
• d.A slipping clutch disc that cannot hold torque in the higher gears

A failing wheel bearing drones and the noise changes as cornering loads shift onto or off of it, helping identify which side. A road test with gentle sway maneuvers isolates it. Play or roughness is confirmed with the wheel raised.

On a serviceable tapered wheel bearing, correct preload is set by:

• a.Leaving the spindle nut only finger tight and installing the cotter pin
• b.Tightening the spindle nut as tight as an impact gun can drive it
• c.Seating the bearing, then backing off and adjusting per spec✓
• d.Using a lock washer alone with no specified torque on the nut

Adjustable tapered bearings are seated, then set to a slight preload or endplay following the procedure so they neither bind nor run loose. Too tight causes overheating; too loose causes play and wander. A cotter pin or lock secures the final setting.

Many modern sealed hub assemblies contain the wheel bearing and also:

• a.The brake master cylinder that supplies pressure to that corner
• b.An integrated wheel-speed sensor for the ABS✓
• c.A fuel pressure regulator that controls delivery to the injectors
• d.The alternator that charges the battery while the engine runs

Sealed hub units combine the bearing, flange, and often the ABS speed sensor or tone ring in one non-serviceable assembly. A bad hub bearing can also set an ABS code if the integrated sensor is affected. The unit is replaced rather than repacked.

After certain tire or wheel services, a tire pressure monitoring system (TPMS) may require a:

• a.Full brake bleed at all four wheels before the vehicle is driven
• b.Relearn so the module recognizes each sensor's position✓
• c.Coolant flush and refill to restore proper engine temperature
• d.Fuel system decarbonizing service to clear the intake passages

Rotating tires or replacing sensors can require a TPMS relearn so the module maps each sensor to its wheel position. Without it, the system may warn or show wrong locations. The procedure varies by manufacturer and tool.

A tire worn on one edge only, with the tread blocks otherwise even, most directly indicates a:

• a.Toe problem, which would instead feather the tread across its width
• b.Camber problem at that wheel✓
• c.Wheel balance problem that would produce a speed-related vibration
• d.Brake problem causing a pull or grab toward that side of the car

Wear concentrated on a single shoulder points to excessive positive or negative camber tilting the tire. Feathered wear across the tread instead indicates a toe error. Correcting the alignment angle stops the wear.

Directional tires marked with a rotation arrow should be rotated so that they:

• a.Stay on the same side, moving front to rear✓
• b.Are dismounted and remounted backward on the wheel each time
• c.Cross over to the opposite side of the vehicle at every rotation
• d.Are never rotated at all to preserve their intended wear pattern

Directional tires must keep their intended rotation direction, so they move front-to-rear on the same side rather than crossing sides. Mounting them backward hurts wet traction and noise. Always follow the correct pattern for the tire type.

A tire's DOT date code is important to check because tires:

• a.Change their physical size and diameter noticeably as they get older
• b.Age and can deteriorate even with adequate tread✓
• c.Gain load-carrying capacity the longer they remain in service
• d.Require no age consideration as long as the tread is still legal

Rubber ages and can crack or fail regardless of remaining tread, so the DOT week/year code helps judge whether an old tire should be replaced. Old spare tires are a common concern. Age plus condition guide replacement.

Dynamic wheel balancing differs from static balancing in that dynamic balancing corrects for:

• a.Only the up-and-down (vertical) imbalance in a single plane
• b.The tire's inflation pressure relative to the placard value
• c.Both up-and-down and side-to-side imbalance✓
• d.The remaining tread depth measured across the tire's face

Dynamic (spin) balancing places weights to cancel imbalance in two planes, eliminating both hop and shimmy, while static balancing addresses only the vertical plane. Modern balancers do dynamic balancing. Correct balance prevents vibration and cupping.

Mixing a radial tire with a bias-ply tire on the same axle is not recommended because it can cause:

• a.A slow coolant leak from the engine's cooling system passages
• b.Unstable handling from different construction and grip✓
• c.A charging system fault that turns on the battery warning lamp
• d.An evaporative emission leak code from the fuel vapor canister

Radial and bias-ply tires flex and grip differently, so mixing them on an axle produces unpredictable handling. Matching tire type, size, and condition keeps the vehicle stable. Manufacturers specify consistent tires on each axle.

A change in vehicle ride height, such as from sagging springs, affects alignment because it:

• a.Affects only the brakes and leaves the steering angles unchanged
• b.Changes only the tire inflation pressure and nothing else at all
• c.Has no measurable effect on any of the vehicle's alignment angles
• d.Alters camber and toe as the suspension geometry shifts✓

Ride height sets where the suspension sits in its travel, so a sagging spring changes camber and toe and can cause a pull or tire wear. Ride height is checked and corrected before setting alignment angles. Worn springs are replaced first.

Bump steer is a condition in which the:

• a.Brakes grab or release unevenly while driving on a rough road
• b.Tires slowly lose air pressure each time the vehicle hits a bump
• c.Steering wheel locks up whenever the brakes are firmly applied
• d.Wheels steer slightly on their own as the suspension moves✓

Bump steer occurs when suspension travel changes toe, so hitting a bump makes the vehicle dart. It often results from bent parts, wrong ride height, or mismatched tie-rod geometry. Correcting the geometry eliminates the darting.

A shock absorber found leaking oil should be:

• a.Overinflated with compressed air to compensate for the lost oil
• b.Refilled with fresh brake fluid and returned to service on the vehicle
• c.Wiped clean of the leaking oil and simply reinstalled as it was
• d.Replaced, usually in pairs on the same axle✓

A shock leaking its oil has lost damping and should be replaced, and doing both on an axle keeps handling balanced. Worn shocks cause bounce, cupping, and poor control. A quick bounce test and visual leak check confirm the condition.

An air (load-leveling) suspension that will not hold ride height most likely has a:

• a.Leaking air spring, dead compressor, or leaking line✓
• b.Faulty oxygen sensor that has slowed its response in the exhaust
• c.Worn brake pad set that has gone metal-to-metal at one wheel
• d.Clogged fuel injector causing a lean misfire under acceleration

Air suspension holds height by adding air, so a leak in a spring, line, or valve, or a dead compressor lets the vehicle sag. The system is checked for leaks and compressor operation. A height sensor fault can also cause improper leveling.

A vehicle that drifts on a level road but tracks straight on a crowned road may be reacting to:

• a.A boiling master cylinder overflowing brake fluid from the reservoir
• b.An overcharged battery from extra load on the charging system
• c.Road crown rather than a true alignment fault✓
• d.A clogged EGR valve that has begun to affect the engine idle

Roads are crowned for drainage, which can make a properly aligned vehicle drift slightly toward the low side. Distinguishing crown drift from a true pull avoids unnecessary repairs. Swapping tires and checking cross-camber help confirm.

Radial runout of a tire and wheel assembly refers to:

• a.The toe setting of the front wheels measured from above the tire
• b.Side-to-side wobble of the assembly measured across its face
• c.The inward or outward tilt of the tire measured from vertical
• d.Up-and-down (out-of-round) variation as it rotates✓

Radial runout is out-of-roundness that causes a vertical hop, while lateral runout is side-to-side wobble. Excess runout causes vibration that balancing alone will not fix. It is measured with a dial indicator against the tire or rim.

For a hub-centric wheel, the wheel is centered on the hub by the:

• a.Lug nuts alone as they are tightened in the crisscross pattern
• b.Tire bead sealing against the outer lip of the wheel flange
• c.Center bore fitting over the hub's machined pilot✓
• d.Valve stem seating against its hole in the rim of the wheel

A hub-centric wheel locates on the machined hub pilot at its center bore, so the load and centering are carried there while the lugs clamp it. Lug-centric wheels instead center on tapered lug seats. Correct centering prevents vibration.

A steering shimmy that appears at a specific highway speed and smooths above or below it is most often:

• a.A dirty cabin air filter restricting airflow through the HVAC case
• b.A worn oxygen sensor that has slowed its response in the exhaust
• c.A stuck-closed thermostat that raises the engine coolant temperature
• d.Wheel and tire imbalance✓

An imbalance excites a vibration at the speed where the heavy spot's frequency peaks, felt as a shimmy that comes and goes with speed. Balancing corrects it. Runout or a worn part can cause similar symptoms if balancing does not resolve it.

Torque steer, a pull under hard acceleration on a front-wheel-drive car, is most associated with:

• a.A worn brake master cylinder leaking fluid past its internal seals
• b.Unequal drive axle angles or lengths applying torque unevenly✓
• c.A dirty engine air filter restricting airflow into the intake tract
• d.A leaking A/C evaporator dripping refrigerant oil in the HVAC case

Torque steer arises when the front drive axles apply torque unevenly, often due to their differing angles or lengths, pulling the steering during acceleration. Worn mounts or suspension parts can worsen it. It is distinguished from an alignment pull by its throttle sensitivity.

Excessive positive caster on a vehicle without power steering will most noticeably increase:

• a.The vehicle's tendency to wander and drift at highway speed
• b.The likelihood that the wheels will shimmy at a specific speed
• c.Steering effort while improving straight-line stability✓
• d.Tire wear across the center of the tread on both front tires

Positive caster tilts the steering axis rearward at the top, aiding stability and return but raising effort, which is more noticeable without power assist. Too little caster causes wander instead. Caster is compared side to side during alignment.

Technician A says a worn ball joint can produce a clunk and cause a failed alignment. Technician B says a worn ball joint can wear a tire and, if it separates, cause loss of control. Who is correct?

• a.Neither A nor B
• b.Technician B only
• c.Both A and B✓
• d.Technician A only

A worn ball joint clunks, shifts alignment, wears tires, and can fail dangerously if it separates. Both technicians are correct. Worn joints are replaced before performing an alignment.

Technician A says correct toe is critical for even tire wear. Technician B says toe is adjustable on most vehicles. Who is correct?

• a.Neither A nor B
• b.Technician A only
• c.Technician B only
• d.Both A and B✓

Toe strongly affects tire wear and is adjustable on virtually all vehicles. Both technicians are correct. Toe is typically the last angle set during an alignment.

Technician A says a defective (conicity) tire can cause a pull. Technician B says swapping the front tires side to side can help confirm a tire-caused pull. Who is correct?

• a.Technician A only
• b.Neither A nor B
• c.Technician B only
• d.Both A and B✓

A tire with internal conicity can steer the vehicle, and swapping the tires side to side changes or moves the pull, confirming the tire. Both technicians are correct. This test isolates a tire pull from an alignment pull.

R-1234yf, used in newer vehicles instead of R-134a, is notable because it:

• a.Is chemically identical to the older R-12 refrigerant it replaced
• b.Can be freely mixed with R-134a in any proportion without a problem
• c.Requires no special handling, fittings, or recovery equipment at all
• d.Has a much lower global-warming impact and is mildly flammable✓

R-1234yf was adopted for its low global-warming potential, but it is mildly flammable and must not be mixed with other refrigerants. It uses unique fittings and equipment to prevent cross-contamination. Correct identification and handling are required.

The high-side and low-side service ports on a modern A/C system use different fitting sizes so that:

• a.Refrigerant is able to flow through the system at a much faster rate
• b.Equipment cannot be connected to the wrong side✓
• c.The compressor runs at a cooler temperature during heavy cooling loads
• d.Compressor oil is automatically added to the system during operation

Different quick-couple sizes on the high and low sides prevent connecting the manifold set or charging equipment backward. This protects the technician and the system. The ports are also marked H and L.

A manifold gauge set connected to an A/C system is used to:

• a.Check the remaining tread depth on each of the vehicle's tires
• b.Test the vehicle battery's voltage and cold-cranking performance
• c.Read high- and low-side pressures for diagnosis✓
• d.Measure the engine's oil pressure at idle and at operating speed

The manifold gauges show both system pressures, which the technician interprets to judge charge level, restrictions, and component operation. It also controls evacuation and charging. Pressure readings are compared with ambient temperature.

Before recharging an A/C system that has been opened, the system should be:

• a.Pressurized with ordinary compressed shop air to check for leaks
• b.Evacuated with a vacuum pump to remove air and moisture✓
• c.Placed in a freezer overnight to condense the remaining moisture
• d.Filled quickly with refrigerant without pulling any vacuum first

Pulling a deep vacuum removes non-condensable air and lowers the boiling point of any moisture so it evaporates and is drawn out. Moisture left inside forms acids and ice. A proper evacuation precedes charging by weight.

Using the wrong or incompatible compressor oil in an A/C system can cause:

• a.Poor lubrication and compressor damage✓
• b.A stronger and hotter output from the vehicle's cabin heater core
• c.A faster windshield defrost with no effect on the compressor at all
• d.A noticeable increase in the vehicle's overall highway fuel economy

A/C compressors require the specific oil type for their refrigerant; the wrong or contaminated oil breaks down lubrication and can destroy the compressor. PAG and POE oils are matched to system requirements. The correct oil and amount are specified by the manufacturer.

The air gap on a magnetic A/C compressor clutch is important because:

• a.It controls the blower motor speed selected on the HVAC control head
• b.Too large a gap can keep the clutch from engaging✓
• c.It cools the condenser by directing extra airflow across its fins
• d.It sets the exact refrigerant charge weight for the whole system

The clutch engages when the coil pulls the plate across the air gap; if the gap grows too wide, the clutch slips or will not engage. The gap is measured and shimmed to spec. A worn or improperly gapped clutch causes intermittent cooling.

A low-pressure cutout switch in an A/C system protects the compressor by:

• a.Adding more refrigerant into the system automatically when it runs low
• b.Opening the blend-air door to direct additional air over the core
• c.Disengaging the clutch when pressure or charge is too low✓
• d.Increasing the blower motor speed to move more air across the coils

If the charge drops too low, the low-pressure switch cuts the clutch so the compressor is not run without adequate refrigerant and oil circulation. This prevents damage from lack of lubrication. It is a common reason a clutch will not engage.

A high-pressure cutout switch is used to:

• a.Charge the vehicle's battery through the air conditioning system
• b.Shut off the compressor if pressure rises dangerously high✓
• c.Boost the output of the cabin heater when the engine is fully warm
• d.Regulate the flow of engine coolant through the heater core

The high-pressure switch or transducer disengages the clutch or signals the module when pressures climb too high, protecting components from a blocked condenser or overcharge. It works with the fan controls to manage pressure. Excess pressure can rupture parts if unchecked.

In an orifice tube (CCOT) A/C system, the accumulator is located:

• a.On the high-pressure liquid line, before the condenser inlet fitting
• b.Inside the compressor housing between the pistons and the reed valves
• c.Within the heater core assembly on the passenger cabin side of the case
• d.On the low-pressure suction side, after the evaporator✓

The accumulator sits on the suction line in orifice-tube systems to store excess refrigerant and protect the compressor from liquid slugging, and it holds desiccant. A receiver-drier, by contrast, is used on the liquid line of expansion-valve systems. Its location matches the metering device type.

The receiver-drier in a thermostatic expansion valve (TXV) system is located:

• a.Inside the blower motor housing on the passenger side of the case
• b.On the low-pressure suction line just after the evaporator outlet
• c.On the high-pressure liquid line, before the expansion valve✓
• d.Within the radiator core alongside the engine coolant passages

The receiver-drier stores liquid refrigerant and removes moisture on the high side ahead of the TXV, ensuring only liquid reaches the valve. Orifice-tube systems instead use a suction-side accumulator. Matching the component to the system type is important during service.

An evaporator that repeatedly freezes over, cutting off airflow, is often caused by:

• a.A control that fails to cycle the compressor off in time✓
• b.A leaking axle seal letting gear oil reach the brake linings
• c.A worn front wheel bearing that drones and roughens with speed
• d.A cracked engine exhaust manifold ticking loudly on a cold start

If the compressor does not cycle off as the evaporator nears freezing, condensation freezes on the fins and blocks airflow. A thermostat, temperature sensor, or pressure switch normally prevents this. Restoring proper cycling stops the icing.

A blower motor that works only on the highest speed, with lower speeds dead, most likely has:

• a.A stuck blend-air door leaving the vent temperature uncontrollable
• b.A clogged orifice tube restricting refrigerant into the evaporator
• c.A low refrigerant charge that shows low on both service gauges
• d.A failed blower motor resistor or speed control module✓

The resistor pack or solid-state control sets the lower fan speeds, so its failure often leaves only high speed working, which bypasses the resistor. Replacing the resistor or module restores all speeds. A blower that does not run at all points elsewhere.

A stuck blend-air door actuator will most likely cause:

• a.A dead battery that cannot start the vehicle after it sits overnight
• b.A refrigerant leak from the low side that slowly empties the system
• c.A brake pull to one side felt whenever the vehicle is slowed down
• d.Incorrect or uncontrollable vent temperature✓

The blend door meters air across the heater core to set temperature, so a stuck actuator leaves the output stuck hot, cold, or unresponsive to the controls. Actuators can be tested and recalibrated or replaced. Clicking noises often signal a failing actuator.

A dirty or clogged cabin air filter most commonly causes:

• a.Reduced airflow from the dashboard vents✓
• b.A compressor clutch that stays engaged and will not release at all
• c.A sudden high-side pressure spike that trips the cutout switch
• d.A refrigerant overcharge that raises the system's high-side pressure

A restricted cabin filter chokes the air the blower can move, so vent output drops even though the system is otherwise fine. Replacing the filter restores airflow. It also affects both heating and cooling volume.

An A/C performance test is typically evaluated by measuring the:

• a.Engine oil pressure at idle and again at normal operating speed
• b.Battery cold-cranking amps under load with a carbon-pile tester
• c.Vent discharge air temperature plus the system pressures✓
• d.Tire tread depth at several points across each of the four tires

Technicians judge A/C performance by the temperature at the center vent, together with high- and low-side pressures at a known ambient temperature and humidity. These readings reveal charge and component problems. Manufacturer specs give the target vent temperature.

A very low low-side pressure with frost forming at the metering device inlet usually indicates:

• a.A restriction at the orifice tube or expansion valve✓
• b.A worn front wheel bearing that drones and roughens with speed
• c.An overcharge of refrigerant that raises pressure on both service sides
• d.A slipping serpentine belt that cannot fully drive the compressor

A blockage at the orifice or a stuck-closed expansion valve starves the evaporator, dropping low-side pressure and causing localized frost from the pressure drop at the restriction. Cooling suffers because little refrigerant flows. Replacing the metering device or clearing the restriction restores flow.

In a system with a heater control valve, no cabin heat could be caused by the valve being:

• a.Frozen solid by the cold evaporator core mounted next to it
• b.Stuck wide open and sending too much refrigerant into the evaporator
• c.Electrically bypassed by the blower motor speed control resistor
• d.Stuck closed and blocking coolant to the heater core✓

A heater control valve regulates hot coolant to the core; if it sticks closed, no hot coolant reaches the core and there is no heat. A stuck-open valve can make heat hard to shut off. Not all vehicles use such a valve, relying on the blend door instead.

No cabin heat with the engine at normal temperature and a full cooling system is often caused by a:

• a.Low refrigerant charge reading low on both of the service gauges
• b.Clogged heater core or a stuck blend-air door✓
• c.Worn compressor clutch that slips and cannot drive the compressor
• d.Faulty high-pressure cutout switch on the refrigerant high side

With the engine warm and coolant full, a lack of heat points to restricted coolant flow through the core or a blend door not directing air over it. Flushing the core or repairing the actuator restores heat. Refrigerant components affect cooling, not heating.

In an automatic climate control system, the in-car temperature sensor is used to:

• a.Measure refrigerant pressure on the high and low sides of the system
• b.Provide feedback so the system holds the set temperature✓
• c.Read the individual wheel speeds for the traction control system
• d.Sense the engine oil level and warn the driver when it drops low

The in-car sensor tells the module the actual cabin temperature so it can adjust blend, blower, and compressor to hold the setpoint. A faulty or blocked sensor causes poor temperature control. A small aspirator fan often draws air across it.

Refrigerant leaks are commonly located using:

• a.An electronic leak detector or UV dye with a UV light✓
• b.A test light probed across the vehicle battery's positive terminal
• c.A compression tester threaded into each of the engine's spark plug holes
• d.A vacuum gauge connected to a port on the engine's intake manifold

An electronic sniffer or fluorescent dye traced with a UV lamp pinpoints where refrigerant is escaping. The leak must be repaired before recharging. Soap solution can help confirm a suspected spot.

Severe internal compressor failure that spreads metal debris through the system requires:

• a.Flushing or replacing contaminated parts and adding a filter✓
• b.Replacing only the cabin air filter and returning the vehicle to service
• c.Only adding a larger amount of fresh refrigerant to flush the debris out
• d.Simply raising the engine idle speed to spin the new compressor faster

When a compressor comes apart, debris and acid contaminate the system, so the affected parts are flushed or replaced and an inline filter is often added to protect the new compressor. Simply installing a compressor invites repeat failure. Proper cleanup and oil balancing are essential.

The condenser cooling fan should run when the A/C is on because it:

• a.Cools the front brake rotors during repeated hard braking on descents
• b.Charges the vehicle's battery whenever the engine is at operating speed
• c.Provides airflow so the condenser can reject heat✓
• d.Increases the fuel pressure delivered to the engine's fuel injectors

The condenser needs airflow to condense the refrigerant; at idle or low speed the electric fan supplies it, so a fan failure raises high-side pressure and hurts cooling. The module commands the fan based on A/C and pressure inputs. Verifying fan operation is part of A/C diagnosis.

High high-side pressure with normal or low low-side pressure and poor cooling often indicates:

• a.A worn tie rod end introducing play into the vehicle's steering
• b.A low refrigerant charge that reads low on both of the service gauges
• c.A condenser airflow problem or a system overcharge✓
• d.Air that has become trapped inside one of the hydraulic brake lines

Restricted condenser airflow, from a blocked condenser or a dead fan, or an overcharge, raises high-side pressure and reduces cooling. Verifying fan operation, condenser cleanliness, and charge weight isolates it. Correcting airflow or charge normalizes pressures.

Before recovering refrigerant from an unknown system, a technician should:

• a.Add fresh compressor oil to the system to protect the recovery machine
• b.Disconnect the vehicle battery to prevent the compressor from cycling
• c.Run the engine at full throttle to warm the refrigerant before recovery
• d.Check it with a refrigerant identifier for contamination✓

A refrigerant identifier verifies the type and purity so contaminated or mixed refrigerant is not pulled into the shop's clean recovery tank. Cross-contamination ruins equipment and refrigerant. This check protects the machine and future jobs.

An A/C compressor clutch that stays engaged and will not disengage could be caused by a:

• a.Low refrigerant charge that reads low on both of the service gauges
• b.Clogged orifice tube starving the evaporator of liquid refrigerant
• c.Stuck (welded) clutch relay or a control-circuit fault✓
• d.Torn cabin air filter that restricts airflow through the HVAC case

A relay with welded contacts or a shorted control circuit can keep power on the clutch coil so it never releases. Checking the relay and control signal isolates it. A clutch that never disengages can overcool or overwork the system.

A musty or moldy smell when the A/C first turns on is most often caused by:

• a.Microbial growth on the damp evaporator, often from a blocked drain✓
• b.A refrigerant overcharge that raises pressure on both service gauges
• c.A cracked condenser leaking refrigerant into the airflow at the front
• d.A worn compressor clutch that slips under load and cannot engage

Moisture condensing on the cold evaporator can grow mold, producing a musty odor, especially if the condensate drain is blocked and water pools. Cleaning or treating the evaporator and clearing the drain helps. Running the fan to dry the core before shutdown reduces it.

Charging an A/C system by weight (the specified amount) is preferred over charging by pressure because it:

• a.Is required only on older systems that still use R-12 refrigerant
• b.Gives the exact correct charge regardless of conditions✓
• c.Lets the technician ignore the system's rated refrigerant capacity
• d.Uses far less service equipment than any other charging method available

The manufacturer specifies an exact refrigerant weight, and charging to that weight avoids the errors of estimating by pressure, which varies with temperature and humidity. Precise charge maximizes cooling and protects the compressor. A recovery/recharge machine measures the charge accurately.

A cracked or leaking heater core will typically produce:

• a.A refrigerant leak from the low side along with unusually warm vents
• b.A sweet smell, foggy windows, and coolant loss✓
• c.A high, hard brake pedal that requires extra effort to fully stop
• d.An overcharged battery from extra load placed on the alternator

Coolant leaking from the heater core inside the dash fogs the glass with a sweet-smelling film and slowly drops the coolant level. The core is pressure-tested and replaced. A greasy film on the windshield is a classic sign.

The mode (air distribution) doors in the HVAC case control:

• a.Whether air comes from the dash, floor, or defrost outlets✓
• b.The temperature of the engine coolant flowing to the heater core
• c.The exact refrigerant charge weight held within the A/C system
• d.The alternator output that charges the battery while driving

Mode doors direct the conditioned air to the panel, floor, defrost, or a blend of outlets as selected. A stuck mode door or actuator leaves airflow at the wrong vents. They are separate from the blend (temperature) door.

Selecting recirculation mode on the HVAC controls causes the system to:

• a.Add more refrigerant into the system to lower the vent temperature
• b.Draw air from inside the cabin rather than from outside✓
• c.Route the incoming air around the evaporator, bypassing the coil
• d.Increase the engine's idle speed to spin the compressor faster

Recirculation closes the fresh-air door and reuses cabin air, which cools faster on hot days and blocks outside odors. A stuck recirculation door can cause weak defrost or stale air. Fresh-air mode brings in outside air for ventilation and defrosting.

A blower motor that does not run at any speed, with a good fuse, most likely has a:

• a.Failed motor, connector, or control switch or module✓
• b.Stuck expansion valve starving the evaporator of liquid refrigerant
• c.Low refrigerant charge that reads low on both of the service gauges
• d.Clogged condenser restricting airflow at the front of the vehicle

No operation at any speed points to the motor itself, its wiring/connector, or the control circuit rather than the resistor, which affects only lower speeds. Power, ground, and control signal are checked at the motor. A common failure is the motor or a burned connector.

A refrigerant identifier is connected before recovery mainly to protect the shop's:

• a.Recovery machine and refrigerant supply from contamination✓
• b.Engine oil supply from being diluted by refrigerant during the process
• c.Battery charger from an electrical overload while the system runs
• d.Brake fluid reservoir from absorbing moisture out of the humid air

Identifying the refrigerant first prevents pulling sealants, air, or mixed refrigerants into the clean recovery tank and machine. Contamination can ruin the equipment and the recovered supply. It is a quick check that safeguards costly gear.

Technician A says an overcharged A/C system can raise high-side pressure and reduce cooling. Technician B says inadequate condenser airflow can do the same. Who is correct?

• a.Technician B only
• b.Technician A only
• c.Both A and B✓
• d.Neither A nor B

Both an overcharge and poor condenser airflow drive up high-side pressure and hurt cooling. Both technicians are correct. Verifying charge weight and fan operation separates the two causes.

Technician A says refrigerant must be recovered rather than vented. Technician B says a technician handling refrigerant must be certified. Who is correct?

• a.Neither A nor B
• b.Both A and B✓
• c.Technician B only
• d.Technician A only

Regulations require recovering refrigerant with approved equipment and having certified personnel handle it. Both technicians are correct. This protects the environment and ensures proper service.

Technician A says a low refrigerant charge shows low readings on both gauges. Technician B says any leak should be repaired before recharging. Who is correct?

• a.Both A and B✓
• b.Technician B only
• c.Technician A only
• d.Neither A nor B

An undercharge reads low on both sides with weak cooling, and the leak must be fixed before recharging by weight. Both technicians are correct. Dye or an electronic detector locates the leak.

A spark plug removed from one cylinder is dry and coated with dry, black soot, while the others are tan. This most directly indicates that cylinder is running:

• a.lean, because the excess air has scrubbed the insulator clean of any color
• b.cooler than the others because coolant has leaked into that cylinder
• c.rich, with more fuel than can be fully burned✓
• d.exactly at the ideal stoichiometric ratio for that operating condition

Dry, black, sooty carbon on the insulator points to an over-rich mixture in that cylinder, such as a leaking injector or a fault pulling fuel trim positive there. A tan or light-gray insulator is normal. Wet black deposits instead suggest oil, and white blistering suggests overheating.

The heat range of a spark plug refers to how quickly the plug:

• a.can produce a spark once the ignition module has energized the coil
• b.raises the temperature of the incoming air-fuel charge before ignition
• c.develops secondary voltage across its electrode gap under heavy load
• d.transfers combustion heat away from its firing tip to the cylinder head✓

Heat range describes the plug's ability to conduct heat from the tip into the head. A colder plug sheds heat faster and resists pre-ignition in hot engines, while a hotter plug runs the tip warmer to burn off deposits. Using the specified heat range prevents fouling or detonation.

Spark knock (detonation) heard as a metallic pinging under acceleration can be caused by all of the following EXCEPT:

• a.carbon deposits in the chamber that raise the engine's effective compression
• b.a spark plug gap set slightly wider than specification✓
• c.excessive ignition timing that is advanced too far for the fuel being burned
• d.fuel with an octane rating that is lower than what the engine requires

Detonation is uncontrolled combustion after the spark, driven by too much timing, low octane, carbon buildup, overheating, or a lean mixture. A slightly wide plug gap affects spark, not the pressure-and-temperature conditions that cause knock. The knock sensor retards timing to protect the engine.

An ignition coil steps 12 volts up to the tens of thousands of volts needed to fire the plug primarily because of:

• a.the resistance built into the spark plug wire on the secondary output side
• b.the frequency at which the crankshaft position sensor triggers the module
• c.the turns ratio between its primary and secondary windings✓
• d.the size of the air gap designed between the spark plug electrodes

A coil is a transformer: the large turns ratio between the many secondary windings and the few primary windings multiplies the induced voltage when the primary field collapses. This produces the high secondary voltage that jumps the plug gap. Weak primary current lowers available secondary voltage.

In a port fuel-injection system, the quantity of fuel delivered by each injector is controlled mainly by the:

• a.diameter of the fuel return line that carries excess fuel back to the tank
• b.length of time (pulse width) the PCM holds the injector open✓
• c.spring pressure that is set inside the mechanical fuel pressure regulator
• d.resistance value that is printed on the injector's electrical connector

With fuel pressure held relatively constant, the PCM meters fuel by varying injector on-time, called pulse width. Longer pulse width delivers more fuel for acceleration or enrichment. Fuel trims adjust pulse width to keep the mixture near stoichiometric.

Technician A says a clogged or restricted fuel injector can cause a lean misfire on that cylinder. Technician B says a leaking injector can cause a rich condition and hard starting. Who is correct?

• a.Both A and B✓
• b.Technician B only
• c.Technician A only
• d.Neither A nor B

A restricted injector starves its cylinder and causes a lean misfire, while a leaking injector adds extra fuel that riches the mixture and can flood a cylinder on start-up. Both technicians are correct. An injector balance test compares delivery among cylinders.

The theoretically ideal (stoichiometric) air-fuel ratio for a gasoline engine is approximately:

• a.14.7 parts air to 1 part fuel by weight✓
• b.stoichiometry is a diesel-only concept not used on gasoline engines
• c.1 part air to 14.7 parts fuel by weight, the reverse proportion
• d.about 9.0 parts air to 1 part fuel, which is a very rich mixture

Stoichiometric combustion of gasoline occurs near 14.7:1 air to fuel by mass, the ratio at which the three-way catalyst works most efficiently. The PCM uses oxygen-sensor feedback to hold the average close to this value. Richer or leaner operation is used only for specific conditions.

When the engine is cold at start-up, the PCM operates in open loop, meaning it:

• a.shuts off all of the fuel injectors completely until the engine warms up
• b.doubles the ignition timing advance in order to speed up the warm-up
• c.relies only on the downstream oxygen sensor to control the fuel mixture
• d.ignores the oxygen sensor and uses programmed values to set fuel delivery✓

In open loop the oxygen sensors are not yet at operating temperature, so the PCM meters fuel from stored maps based on coolant temperature, load, and rpm. Once the sensors are hot and the engine is warm, it enters closed loop and trims fuel from sensor feedback.

Short-term fuel trim (STFT) differs from long-term fuel trim (LTFT) in that STFT:

• a.controls ignition timing advance and retard rather than fuel delivery
• b.makes rapid, moment-to-moment corrections from oxygen-sensor feedback✓
• c.is calculated only from the mass airflow reading with no feedback loop
• d.is a permanent stored value that can only be cleared with a scan tool

Short-term fuel trim reacts instantly to oxygen-sensor switching, while long-term fuel trim is a learned, slower average that offsets persistent deviations. Reading both together helps distinguish momentary from ongoing mixture problems. Large positive trims indicate the PCM is adding fuel to correct lean operation.

A manifold absolute pressure (MAP) sensor provides the PCM with information about:

• a.engine load, based on intake manifold pressure and vacuum✓
• b.the mass of the air flowing past a heated sensing element in the intake
• c.the exact rotational position of the camshaft during each engine cycle
• d.the amount of oxygen left in the exhaust after the catalytic converter

A MAP sensor reports manifold pressure, which reflects engine load in a speed-density fuel strategy. High vacuum (low pressure) indicates light load, while low vacuum (near atmospheric) indicates heavy load. A faulty MAP signal skews fuel and timing calculations.

An intake air temperature (IAT) sensor is used by the PCM to:

• a.measure the temperature of the engine coolant as it leaves the head
• b.correct fuel and timing for the density of the incoming air✓
• c.regulate the fuel pressure that is maintained inside the injector rail
• d.count the engine's revolutions in order to drive the tachometer

Because cold air is denser and carries more oxygen than warm air, the IAT reading lets the PCM fine-tune fuel delivery and spark for air density. A sensor reading falsely warm can lean the mixture. It works together with the MAF or MAP input.

A wide-band (air-fuel ratio) oxygen sensor has an advantage over a conventional narrow-band sensor because it:

• a.can measure how rich or lean the mixture is across a wide range✓
• b.reports exhaust gas temperature to the PCM instead of oxygen content
• c.reaches full operating temperature without needing any heater circuit
• d.produces a usable signal only when the mixture is exactly 14.7 to 1

A narrow-band sensor mainly switches high or low around stoichiometric, while a wide-band sensor reports the actual air-fuel ratio over a broad span. This gives the PCM finer fuel control and faster, more precise diagnostics. Both types still require heaters for quick activation.

The downstream (post-catalyst) oxygen sensor is used mainly to:

• a.measure the temperature of the exhaust stream ahead of the catalyst
• b.command and control the engine's idle speed under the PCM's direction
• c.monitor how well the catalytic converter stores and releases oxygen✓
• d.provide the primary fuel-trim feedback the PCM uses for the injectors

The rear oxygen sensor watches the exhaust after the catalyst; a healthy converter smooths out the oxygen swings so the rear signal stays fairly steady. When the rear sensor begins to mirror the front, catalyst efficiency has dropped and a P0420-type code may set. The front sensor handles fuel trim.

A three-way catalytic converter reduces tailpipe emissions by:

• a.trapping soot particles from the exhaust the way a diesel filter does
• b.cooling the exhaust gases so fewer emissions can form farther downstream
• c.storing unburned fuel from the exhaust for reuse on the next cold start
• d.oxidizing HC and CO while reducing NOx into harmless gases✓

The three-way catalyst oxidizes hydrocarbons and carbon monoxide into water and carbon dioxide and reduces oxides of nitrogen into nitrogen and oxygen. It works best when the mixture is held near stoichiometric. Misfires, oil, or coolant contamination can overheat and destroy it.

Technician A says a persistent engine misfire can overheat and damage the catalytic converter. Technician B says a flashing malfunction indicator lamp (MIL) warns of a misfire severe enough to harm the catalyst. Who is correct?

• a.Neither A nor B
• b.Technician A only
• c.Both A and B✓
• d.Technician B only

Raw fuel from a misfire ignites in the catalyst and drives its temperature high enough to cause damage, and the PCM flashes the MIL to warn of that catalyst-damaging misfire. Both technicians are correct. The vehicle should be driven gently or stopped until the misfire is repaired.

A P0171 code (system too lean, bank 1) could be caused by any of the following EXCEPT:

• a.a contaminated mass airflow sensor that under-reports the incoming air
• b.low fuel pressure caused by a weak fuel pump or a restricted filter
• c.a leaking fuel injector adding extra fuel to the cylinders✓
• d.an unmetered vacuum leak downstream of the mass airflow sensor

A lean code results from too much air or too little fuel: vacuum leaks, low fuel pressure, or an under-reporting MAF all lean the mixture. A leaking injector adds fuel and would cause a rich condition instead. Checking fuel trims and fuel pressure narrows the cause.

A P0300 (random/multiple-cylinder misfire) code, as opposed to a single-cylinder code, more often points to a problem that is:

• a.common to several cylinders, such as fuel pressure or a vacuum leak✓
• b.isolated to a single coil-on-plug ignition coil on one cylinder
• c.caused only by one leaking or restricted fuel injector
• d.limited to one fouled or worn spark plug on a single cylinder

Because P0300 reports misfires spread across cylinders, the cause is usually something they share: low fuel pressure, a large vacuum leak, EGR flooding the intake, or a weak ignition supply. A single-cylinder code like P0301 points to that cylinder's plug, coil, or injector. Fuel-trim and freeze-frame data guide the diagnosis.

The EVAP purge valve (canister purge solenoid) controls:

• a.the fuel pressure that is maintained in the rail during acceleration
• b.the recirculation of exhaust gas back into the intake manifold for NOx
• c.the flow of stored fuel vapor from the charcoal canister into the intake✓
• d.the amount of fresh air that enters the engine through the throttle body

The purge valve meters fuel vapor from the EVAP canister into the intake to be burned when conditions allow. A valve stuck open acts like a vacuum leak and can cause rough idle or stalling. A stuck-closed valve prevents purging and can set an EVAP flow code.

Fuel trims that read strongly positive at idle but return close to zero at higher rpm most likely indicate:

• a.a vacuum leak whose effect is diluted as airflow increases✓
• b.a mass airflow sensor that over-reports the incoming airflow at idle
• c.a restricted exhaust system that builds up backpressure at higher speed
• d.a leaking fuel injector that keeps riching the mixture only at idle

A fixed-size vacuum leak adds a large percentage of unmetered air at idle when total airflow is low, driving fuel trim positive; at higher rpm that same leak is a small fraction of total flow, so trim normalizes. This rpm-dependent pattern is a classic vacuum-leak fingerprint. Smoke testing helps locate it.

Before an OBD-II vehicle can pass a state emissions inspection, its readiness monitors generally must be:

• a.run to completion, showing 'ready' or 'complete' status✓
• b.cleared to zero by disconnecting the battery just before the inspection
• c.ignored entirely, because the monitors have no bearing on the inspection
• d.forced into a 'not ready' state on purpose using a scan tool command

Readiness monitors are self-tests the PCM runs during specific drive conditions; most programs require them complete so the system can confirm emissions components work. Clearing codes or disconnecting the battery resets monitors to 'not ready,' which can fail an inspection until a drive cycle is completed. A specific drive cycle sets them.

The idle air control (IAC) valve on a cable-throttle engine is used to:

• a.adjust the ignition timing advance during closed-throttle idle operation
• b.meter fuel directly into the intake ports whenever the engine idles
• c.open a passage that recirculates exhaust gas into the intake at idle
• d.regulate airflow bypassing the throttle plate to control idle speed✓

The IAC valve opens or closes a passage that lets air bypass the closed throttle plate, letting the PCM raise idle for cold start or accessory loads and lower it when warm. A dirty or sticking IAC causes unstable or stalling idle. Electronic-throttle engines control idle by moving the throttle plate itself.

On an electronic throttle control (drive-by-wire) system, the PCM verifies driver intent using:

• a.the vehicle speed sensor signal, from which it infers pedal demand
• b.two accelerator-pedal position sensors that must agree with each other✓
• c.only the mass airflow sensor reading with no separate pedal confirmation
• d.a mechanical cable linked directly from the pedal to the throttle plate

Drive-by-wire uses redundant accelerator-pedal position sensors and redundant throttle-position sensors so the PCM can cross-check the signals for safety. If the sensors disagree, the system enters a reduced-power or limp mode. This redundancy replaces the old mechanical throttle cable.

Freeze-frame data stored by the PCM is valuable because it records:

• a.a continuous real-time video recording of all the sensor waveforms
• b.the operating conditions present at the moment a fault was detected✓
• c.a running history of every trouble code the vehicle has ever set
• d.the vehicle owner's complete maintenance and repair service records

Freeze frame captures a snapshot of parameters such as rpm, load, coolant temperature, and fuel trim when the code set, helping recreate the fault conditions. Reviewing it guides the technician toward when and why the problem occurs. It is especially useful for intermittent faults.

Ignition timing that is excessively retarded from specification will most likely cause:

• a.an abnormally high idle speed even with the throttle held fully closed
• b.dieseling or run-on that continues after the ignition key is shut off
• c.engine knock and pinging that occurs mainly under a light-throttle load
• d.reduced power, poor fuel economy, and possible overheating✓

Retarded timing fires the mixture too late, wasting energy as heat in the exhaust, which lowers power and economy and can overheat the engine. Over-advanced timing, by contrast, tends to cause knock. Modern engines set base timing by the PCM using the crank sensor.

Technician A says an EGR valve stuck open can cause a rough idle or stalling. Technician B says an EGR valve stuck closed can allow combustion temperatures to rise and increase NOx. Who is correct?

• a.Neither A nor B
• b.Technician B only
• c.Both A and B✓
• d.Technician A only

Exhaust gas recirculation dilutes the intake charge to lower peak combustion temperature; stuck open at idle it acts like a vacuum leak and causes rough idle or stalling, while stuck closed it lets temperatures and NOx climb. Both technicians are correct. EGR faults commonly set flow-related DTCs.

A restricted exhaust system, such as a plugged catalytic converter, typically produces which driveability symptom?

• a.a rough idle at low rpm that smooths out as engine speed increases
• b.hard starting that appears only during very cold outside weather
• c.loss of power that worsens at higher engine speeds✓
• d.a steady misfire at idle that completely disappears under load

A clogged converter or crushed pipe raises backpressure, choking the engine most at high rpm when it needs to move the most exhaust, so power fades as speed climbs. A backpressure or vacuum test helps confirm restriction. Overheating from a rich condition or misfire is a common cause of a melted converter.

An engine coolant temperature (ECT) sensor that reads colder than the engine actually is will most likely cause:

• a.an overly rich mixture and poor fuel economy✓
• b.the electric cooling fan to run constantly at high speed while cold
• c.reduced ignition coil dwell time and a correspondingly weak spark
• d.a lean mixture with excess air causing a lean misfire at idle

The PCM enriches the mixture when it believes the engine is cold, so a sensor stuck reading low keeps the engine in warm-up enrichment, wasting fuel and fouling plugs. It may also delay closed-loop operation. A sensor reading falsely hot has the opposite effect.

Excessive carbon monoxide (CO) in the exhaust of a gasoline engine most directly indicates:

• a.a rich air-fuel mixture with incomplete combustion✓
• b.a very lean air-fuel mixture that leaves excess oxygen in the exhaust
• c.coolant that is leaking past the head gasket into the combustion chamber
• d.an ignition system that is firing the spark plugs far too early

High CO is a product of incomplete combustion from too much fuel, so it is a rich-mixture indicator. High hydrocarbons point to misfire or unburned fuel, while high NOx points to high combustion temperature. Gas-analyzer readings help pinpoint the fault.

High oxides of nitrogen (NOx) in the exhaust are most closely associated with:

• a.a very rich air-fuel mixture with too much fuel at idle
• b.excess engine oil being drawn into and burned in the chamber
• c.low engine compression on one cylinder from a burned valve
• d.abnormally high combustion temperatures✓

NOx forms when combustion temperatures climb high enough to combine nitrogen and oxygen, so causes include a lean mixture, a non-functioning EGR system, or engine overheating. Recirculating exhaust lowers peak temperature and NOx. A cooling-system or EGR fault is a common contributor.

The camshaft position (CMP) sensor signal is used by the PCM primarily to:

• a.control the position of the electronic drive-by-wire throttle plate
• b.measure the mass of the air that is entering the intake manifold
• c.identify which cylinder is on compression for sequential injection✓
• d.monitor the oxygen-storage efficiency of the catalytic converter

The camshaft sensor tells the PCM cylinder identification and cam timing so it can fire injectors sequentially and time the coils correctly. Paired with the crankshaft sensor, it also detects cam-to-crank correlation problems from timing-chain wear. A lost CMP signal can cause a no-start or extended crank.

A variable valve timing (VVT) system uses an oil control solenoid to:

• a.vary camshaft timing by directing oil pressure to a cam phaser✓
• b.change the cylinder firing order under heavy engine load conditions
• c.regulate the fuel-rail pressure delivered during hard acceleration
• d.open a bypass passage around the throttle plate during warm idle

VVT advances or retards the camshaft by using PCM-controlled oil pressure through a solenoid to move a cam phaser. Low or dirty oil, or a stuck solenoid, can set VVT performance codes and hurt driveability. Correct oil level and viscosity are important for proper operation.

Technician A says a PCV valve stuck open can act like a vacuum leak and lean the mixture. Technician B says a plugged PCV system can cause oil leaks and sludge. Who is correct?

• a.Neither A nor B
• b.Technician B only
• c.Technician A only
• d.Both A and B✓

A PCV valve stuck open lets extra unmetered air into the intake, which the PCM sees as a lean condition, while a plugged system traps blow-by pressure that pushes past seals and promotes sludge. Both technicians are correct. The PCV system should be checked when diagnosing lean codes or oil leaks.

A flooded engine that cranks but will not start after repeated attempts can often be cleared by:

• a.cranking with the throttle held fully closed while cycling the key on and off
• b.pumping the throttle pedal rapidly several times just before cranking
• c.spraying a little water into the throttle body to wash the excess fuel out
• d.holding the throttle wide open while cranking to enter clear-flood mode✓

Most PCMs enter a clear-flood mode that cuts injector pulse width when the throttle is held wide open during cranking, letting excess fuel clear. Pumping a fuel-injected throttle does not add fuel and can worsen flooding. Once it starts, the mixture returns to normal control.

A technician suspects no spark on a coil-on-plug engine. The best tool to confirm the presence of spark is:

• a.a fuel pressure gauge teed into the engine's fuel supply rail
• b.a vacuum gauge connected to a port on the intake manifold
• c.a cooling-system pressure tester attached to the radiator filler neck
• d.a spark tester connected in place of the plug✓

A spark tester provides a calibrated gap to verify that the coil produces a strong spark under compression-like load. Simply pulling a plug wire can give a misleading result and risks a shock. Once spark is confirmed or ruled out, the technician checks the coil, driver, and triggering sensors.

A knock (detonation) sensor is best described as a device that:

• a.counts the crankshaft revolutions used to drive the dashboard tachometer
• b.detects engine vibration frequencies caused by abnormal combustion✓
• c.reports intake manifold vacuum and engine load conditions to the PCM
• d.measures the temperature of the exhaust manifold near the exhaust port

The knock sensor is a piezoelectric device tuned to the vibration frequency of detonation; when it senses knock, the PCM retards timing to protect the engine. A faulty sensor or wiring can cause reduced power from unnecessary timing retard or unheard knock. Torque specification matters when installing it.

Black smoke from the tailpipe of a gasoline engine most directly indicates:

• a.coolant leaking past a head gasket into the combustion chamber
• b.an excessively rich air-fuel mixture✓
• c.engine oil being drawn past the rings and burned in the cylinders
• d.normal water-vapor condensation seen briefly on a cold morning start

Black smoke is unburned fuel from a rich mixture, caused by faults such as leaking injectors, high fuel pressure, or a false-cold coolant sensor. White smoke suggests coolant, and blue suggests oil. A gas analyzer confirms high CO and HC with a rich condition.

A vacuum leak at the intake manifold typically causes an idle that is:

• a.unaffected because idle is entirely computer-controlled
• b.high or rough because of the extra unmetered air✓
• c.low and smooth because the mixture becomes noticeably richer
• d.normal until the engine reaches full operating temperature

Unmetered air from a vacuum leak leans the idle mixture and can raise or destabilize idle speed, and fuel trims go positive to compensate. Smoke testing or spraying a small amount of throttle-body cleaner near suspect areas helps locate it. Idle strategy tries to compensate but often cannot fully mask the leak.

Low fuel pressure caused by a weak pump or clogged filter most commonly produces which driveability complaint?

• a.a high, surging idle speed that will not settle down to normal
• b.engine knock and pinging that occurs only during cold engine starts
• c.excessive blue exhaust smoke that appears mainly on deceleration
• d.hesitation, lack of power, and lean misfire under load✓

When demand is high, low fuel pressure cannot supply enough fuel, so the engine hesitates, lacks power, and may lean-misfire under load. A fuel pressure gauge and volume test confirm supply. A restricted filter or failing pump are common causes.

The crankshaft position sensor and camshaft position sensor together allow the PCM to detect:

• a.the temperature of the intake air charge entering the engine
• b.the amount of fuel remaining in the vehicle's fuel tank
• c.the oxygen-storage efficiency of the catalytic converter
• d.timing-chain wear through a cam-to-crank correlation error✓

By comparing crankshaft and camshaft signals, the PCM verifies valve timing; a stretched timing chain shifts the relationship and sets a correlation code. This can cause rough running and reduced power. Verifying mechanical timing may be required after a correlation DTC.

An engine that starts and runs briefly, then stalls, and will restart only after sitting, may be exhibiting a classic symptom of:

• a.a single fouled spark plug that is causing one steady misfire
• b.a slightly loose gas cap that has set a small EVAP system code
• c.a failing crankshaft position sensor that drops out when hot✓
• d.a worn serpentine drive belt that is slipping under electrical load

A crank sensor that fails when it heats up can cut the signal, stalling the engine until it cools enough to work again. Testing while heating the sensor or watching rpm data during the stall helps confirm it. Heat-related intermittent sensor faults are a common driveability puzzle.

Technician A says a mass airflow sensor that under-reports airflow will make the mixture lean. Technician B says cleaning a contaminated MAF sensor with an approved cleaner can restore accurate readings. Who is correct?

• a.Both A and B✓
• b.Neither A nor B
• c.Technician B only
• d.Technician A only

A MAF that reads low tells the PCM less air is entering than truly is, so it under-fuels and leans the mixture, and dirt on the sensing element is a frequent cause that MAF-specific cleaner can correct. Both technicians are correct. Never touch or scrub the delicate sensing wire.

A gasoline engine that fails an emissions test for high hydrocarbons (HC) is most likely experiencing:

• a.a misfire leaving unburned fuel in the exhaust✓
• b.high combustion temperatures that are forming oxides of nitrogen
• c.a lean air-fuel mixture that leaves excess air but burns cleanly
• d.completely normal operation that is well within all emission limits

Hydrocarbons are unburned fuel, so high HC points to a misfire from ignition, fuel, or compression faults, or a failing catalyst. High CO indicates a rich mixture, while high NOx indicates high temperature. Finding and fixing the misfire lowers HC.

The purpose of the secondary air injection system on some vehicles is to:

• a.recirculate exhaust gas back into the intake to help lower NOx
• b.add extra fuel into the exhaust to raise catalyst temperature at idle
• c.add air to the exhaust so the catalyst warms and oxidizes emissions faster✓
• d.cool the exhaust manifold and downpipe during periods of heavy load

Secondary air injection pumps fresh air into the exhaust during cold start so extra oxygen helps oxidize HC and CO and warms the catalyst quickly. A stuck valve or failed pump can set related codes. It operates only briefly after start-up.

A cylinder with very low compression will most likely cause:

• a.an abnormally high charging-system voltage from the alternator
• b.a false lean trouble code being set on the opposite cylinder bank
• c.a misfire and rough running on that cylinder✓
• d.a rich air-fuel mixture affecting all of the cylinders at once

Low compression means that cylinder cannot make normal power, producing a misfire and rough idle. Causes include burned valves, worn rings, or a blown head gasket, confirmed with a compression or leak-down test. The misfire may set a cylinder-specific code.

Ethanol content in gasoline matters to the fuel system because ethanol:

• a.removes any need for oxygen-sensor feedback in the fuel-control system
• b.cannot be detected or compensated for in any way by the PCM
• c.changes the stoichiometric ratio, so flex-fuel systems adjust fueling✓
• d.raises the fuel pressure inside a sealed tank entirely on its own

Ethanol requires a richer air-fuel ratio than straight gasoline, so flex-fuel vehicles use a fuel composition sensor or fuel-trim learning to add fuel as ethanol content rises. Incorrect fuel can cause lean or rich operation. Fuel-system materials are chosen to resist ethanol.

A P0442 (small EVAP leak) code is frequently caused by:

• a.a worn crankshaft position sensor that intermittently drops its signal
• b.a loose, damaged, or missing fuel cap✓
• c.low fuel pressure at the injector rail during heavy acceleration
• d.a failed catalytic converter substrate that has broken apart inside

A small EVAP leak commonly traces to a fuel cap that is loose, cracked, or has a bad seal, letting vapor escape. The system checks itself by pressurizing or applying vacuum and watching for decay. Tightening or replacing the cap often clears it after a drive cycle.

An injector balance test is used to:

• a.check the oxygen-storage efficiency of the catalytic converter
• b.compare fuel delivery among injectors by measuring pressure drop✓
• c.measure the electrical resistance of the ignition coil primary winding
• d.verify the internal calibration of the mass airflow sensor element

Pulsing each injector for the same time and comparing the fuel-rail pressure drop, or the rpm change from cylinder power balance, reveals a weak or leaking injector. A cylinder that differs sharply signals a fueling problem. This isolates a mechanical injector fault from other misfire causes.

Spark plug gap is important because a gap that is too wide will:

• a.raise the effective compression pressure inside that cylinder
• b.fire the mixture far too easily and rapidly foul the plug with raw fuel
• c.require more voltage to fire and can cause misfires under load✓
• d.lower peak combustion temperature and reduce the formation of NOx

A wider gap needs higher secondary voltage to jump; if the coil cannot supply it under load, the plug misfires. Too small a gap gives a weak spark that may not reliably ignite the mixture. Setting the specified gap ensures consistent ignition.

Technician A says an engine that runs well cold but stumbles once warm may have a coolant temperature sensor or fuel-delivery fault. Technician B says scan-tool live data helps confirm which sensor reading is out of range. Who is correct?

• a.Both A and B✓
• b.Technician A only
• c.Neither A nor B
• d.Technician B only

A warm stumble can come from a sensor whose reading shifts with temperature or from fuel delivery that falls off when hot, and comparing live data to known-good values pinpoints the offending signal. Both technicians are correct. Freeze-frame and fuel-trim data guide the diagnosis.

The oxygen sensor heater circuit is important because it:

• a.brings the sensor to operating temperature so closed loop begins sooner✓
• b.measures the exhaust backpressure present at the sensor
• c.produces the sensor's output voltage signal all by itself
• d.cools the sensor to protect it from exhaust heat damage

A built-in heater lets the oxygen sensor reach its roughly 600-degree operating temperature soon after start-up, so the engine enters closed loop and reduces emissions faster. A failed heater sets a heater-circuit code and delays closed loop. The heater is a separate circuit from the sensing element.

A vehicle sets a P0128 (coolant temperature below thermostat regulating temperature) code most often because:

• a.the radiator pressure cap is holding far too much system pressure
• b.the water pump is circulating the coolant far too quickly to warm it
• c.the electric cooling fan never turns on at any coolant temperature
• d.the thermostat is stuck open and the engine never fully warms✓

P0128 means the engine did not reach expected temperature in the expected time, and a thermostat stuck open is the usual cause, letting coolant flow before warm-up is complete. This wastes fuel and delays full closed-loop efficiency. Verifying warm-up with a scan tool confirms the fault.

Mode 6 data on an OBD-II scan tool is useful because it shows:

• a.a live oscilloscope trace of the current through each ignition coil
• b.the vehicle's complete repair and maintenance service history
• c.the exact street location where the diagnostic code first set
• d.the results and limits of the PCM's non-continuous self-tests✓

Mode 6 reports the pass/fail test values and thresholds behind the readiness monitors, such as catalyst and EVAP tests, so a technician can spot a component trending toward failure before a code sets. Reading it alongside freeze frame aids diagnosis. Test IDs must be matched to the vehicle's definitions.

A dirty or sticking throttle body can cause a driveability complaint of:

• a.a steady high-speed vibration that is felt through the driver's seat
• b.an excessively high charging voltage seen at highway cruising speed
• c.unstable idle, stalling, or hesitation from restricted airflow✓
• d.engine knock that appears only under very heavy acceleration

Carbon buildup on the throttle bore and plate disturbs the small airflow that controls idle, causing rough idle, stalling, or tip-in hesitation. Cleaning the throttle body and, on some vehicles, performing an idle relearn restores normal operation. Electronic throttles may need a relearn after cleaning.

When diagnosing a misfire, performing a cylinder power balance test helps by:

• a.identifying which cylinder contributes least to engine output✓
• b.testing the state of charge and condition of the vehicle's battery
• c.measuring the precise octane rating of the fuel in the tank
• d.checking the front-wheel alignment angles such as camber and toe

A power balance test disables cylinders one at a time (or uses scan-tool misfire counts) to find the weak cylinder by its small effect on rpm. The cylinder that changes engine speed the least is the suspect. Follow-up compression, injector, and ignition tests find the root cause.

A restricted or plugged fuel injector on one cylinder, compared with a leaking injector, is more likely to cause:

• a.an overcharging condition in the vehicle's charging system
• b.black exhaust smoke coming from all of the cylinders under load
• c.a lean misfire and hesitation from that one cylinder✓
• d.a rich condition and hard starting that affects the whole engine

A restricted injector delivers too little fuel to its cylinder, leaning it out and causing a misfire or hesitation, while a leaking injector adds fuel and riches the mixture. Comparing symptoms helps direct the diagnosis. An injector balance or flow test confirms which injector is at fault.

A battery's cold cranking amps (CCA) rating specifies the current it can deliver:

• a.at 80 degrees Fahrenheit for a full 60 minutes of continuous discharge
• b.for exactly 15 seconds at normal room temperature under any load
• c.at 0 degrees Fahrenheit for 30 seconds while staying above 7.2 volts✓
• d.only after the charging system has brought it up to a full charge

CCA measures how many amps a fully charged battery can supply at 0 F for 30 seconds while staying at or above 7.2 volts, reflecting cold-start ability. A battery must meet or exceed the vehicle's CCA requirement. Cold weather reduces available cranking power.

A battery's reserve capacity rating indicates how long it can:

• a.accept a charge from the alternator when it is deeply discharged
• b.be stored on a shelf before it will need to be recharged again
• c.supply a set current to run essential loads if the charging system fails✓
• d.deliver its full cold cranking amps rating in freezing weather

Reserve capacity is the minutes a fully charged battery can supply about 25 amps at 80 F while holding above 10.5 volts, showing how long it could run the vehicle with a dead charging system. It complements the CCA rating. A higher number means more backup run time.

A conventional battery capacity (load) test is typically performed by loading the battery to about:

• a.one-half its CCA rating for 15 seconds while watching the voltage✓
• b.the alternator's maximum rated output current for five minutes
• c.its full rated reserve capacity continuously for one full hour
• d.twice its CCA rating for 30 seconds while the engine is cranking

A load test draws roughly half the CCA for 15 seconds; a good battery stays above about 9.6 volts at 70 F. The battery must be adequately charged first for a valid result. Electronic conductance testers estimate capacity without a heavy load.

On a battery with removable caps, a hydrometer measures state of charge by reading the:

• a.internal resistance of the lead plates inside each individual cell
• b.specific gravity of the electrolyte in each cell✓
• c.temperature of the electrolyte without regard to its density
• d.open-circuit voltage measured across the battery's two terminals

A hydrometer measures electrolyte specific gravity, which rises with charge; about 1.265 indicates full charge in a healthy cell. A large variation between cells indicates a defective battery. Readings are temperature-corrected for accuracy.

An absorbed glass mat (AGM) battery differs from a conventional flooded battery in that it:

• a.contains no lead plates whatsoever in its internal construction
• b.is self-charging internally and needs no charging system at all
• c.must always be installed in a completely upside-down position
• d.holds its electrolyte in glass mats, resisting spills and vibration✓

In an AGM battery the electrolyte is absorbed into fiberglass mats between the plates, making it spill-resistant and more vibration-tolerant. AGM batteries often require a charger setting matched to their chemistry. Using the wrong high charging voltage can shorten their life.

In a series circuit with two loads, the source voltage is:

• a.applied at its full value across each of the two loads
• b.present only across the first load, with none reaching the second
• c.divided among the loads in proportion to their resistances✓
• d.doubled at the second load compared with the first load in line

In a series circuit the same current flows through all loads and the total source voltage is split among them according to each resistance. Adding the individual voltage drops equals the source voltage. This is the basis of voltage-drop testing.

Three resistors of 2, 3, and 5 ohms wired in series produce a total resistance of:

• a.3.33 ohms, taking the simple average of the three resistor values
• b.30 ohms, obtained by multiplying the three resistor values together
• c.10 ohms✓
• d.0.97 ohms, as if the three resistors were connected in parallel

Series resistances add directly, so 2 + 3 + 5 equals 10 ohms. Total series resistance is always larger than any single resistor. This raises total resistance and reduces circuit current for a given voltage.

In a parallel circuit, the voltage across each branch is:

• a.the same and equal to the source voltage✓
• b.zero in every branch except the first one in the circuit
• c.different for every branch according to the design intent
• d.divided equally among the branches so each sees one-third

Each branch of a parallel circuit connects directly across the source, so every branch sees the same voltage. Current, however, divides among the branches according to each resistance. Automotive lighting and accessory circuits are wired in parallel so each works independently.

A 'short to ground' fault in an automotive circuit means the current:

• a.flows backward from the ground toward the battery's positive post
• b.finds an unintended low-resistance path directly to ground✓
• c.is safely limited by an added resistor placed in the circuit
• d.cannot flow at all because the wire has become completely open

A short to ground bypasses the intended load through a low-resistance path, drawing high current that usually blows the fuse. It differs from an open, which stops current entirely. Inspecting for chafed insulation against metal helps locate it.

Unwanted high resistance from a corroded connection in a circuit will:

• a.have no measurable effect on how the circuit operates
• b.raise the source voltage that the battery produces
• c.cause a voltage drop and reduced current, often heating the joint✓
• d.increase the current that flows through the affected circuit

High resistance at a corroded or loose connection consumes voltage the load needs, dimming lights or slowing motors, and the resistance can heat the joint. A voltage-drop test across the connection reveals it. Cleaning and tightening restores normal operation.

An ohmmeter measures resistance or continuity, and it must always be connected to a circuit that is:

• a.de-energized, with no power applied✓
• b.fully powered and operating so that current is actively flowing
• c.connected to a running charging system that is supplying voltage
• d.cranking the engine over at the moment the reading is taken

An ohmmeter supplies its own small test current, so applying it to a live circuit gives false readings and can damage the meter. The circuit must be off and often isolated. A reading of near zero ohms indicates continuity; infinite ohms indicates an open.

An ammeter is connected in series with a load, and it is designed to have:

• a.no effect at all because it senses only the surrounding magnetic field
• b.the same resistance value as the load that is being measured
• c.very low internal resistance so it does not restrict current✓
• d.very high internal resistance, just like a voltmeter, so it blocks current

An ammeter carries the circuit current, so it must have very low internal resistance to avoid altering the reading or the circuit. It is placed in series in the current path. A clamp-type ammeter instead reads current by sensing the magnetic field, without breaking the circuit.

A fusible link differs from a blade fuse in that it:

• a.carries no current at all under normal operating conditions
• b.is a length of smaller wire that melts to protect high-current circuits✓
• c.automatically resets itself after it has been given time to cool
• d.increases the amount of amperage available to the circuit

A fusible link is a short section of smaller-gauge wire with heat-resistant insulation that melts open to protect main power feeds carrying heavy current. Unlike a self-resetting breaker, a blown link must be replaced. It is typically located near the battery or main junction.

A self-resetting (cycling) circuit breaker is often used for circuits such as power windows because it:

• a.increases the voltage supplied to the motor when it trips
• b.never opens at all regardless of how much current flows through it
• c.must be manually replaced by hand every time that it trips open
• d.opens under an overload and closes again after it cools✓

A cycling breaker protects motors that may briefly overload by opening on high current and resetting as it cools, avoiding repeated fuse replacement. This suits windows, wipers, and seats. A repeated trip still signals an underlying fault to repair.

The starter solenoid on a typical starter performs two jobs: it engages the drive pinion and it:

• a.regulates the charging voltage that is sent back to the battery
• b.measures the amount of current that is drawn during cranking
• c.rectifies the alternator's alternating current into usable direct current
• d.closes the high-current contacts that feed the starter motor✓

The solenoid both pushes the pinion into the flywheel ring gear and closes heavy contacts that connect battery current to the motor. A weak solenoid or burned contacts can cause a click with no crank. It is controlled by the low-current start circuit.

A starter current-draw test that shows excessive amperage during cranking most likely indicates:

• a.a binding engine or a worn starter with internal drag✓
• b.a completely discharged battery with an open internal circuit
• c.a normal, perfectly healthy cranking condition with no fault
• d.an open somewhere in the low-current starter control circuit

Higher-than-specified starter draw points to mechanical drag, such as a worn starter, tight bearings, or a binding engine, forcing the motor to work harder. Low draw with slow cranking instead suggests high resistance. Comparing draw to specification guides the diagnosis.

A neutral safety switch (or clutch position switch) is designed to:

• a.prevent the starter from operating unless in Park/Neutral or clutch pressed✓
• b.cut off the charging voltage any time the engine is switched off
• c.disable the fuel pump whenever the vehicle's doors are unlocked
• d.turn off the headlights automatically whenever the vehicle is parked

The neutral safety switch completes the start circuit only in Park or Neutral (or with the clutch pressed) so the vehicle cannot lurch when started. A faulty switch can cause a no-crank in Park that cranks in Neutral, or vice versa. It is a common no-crank diagnostic point.

A single loud click from the starter solenoid with no cranking, and dim lights, most likely indicates:

• a.a fully charged battery paired with a completely healthy starter
• b.an open in the fuel-injector control circuit
• c.a short to ground somewhere in the headlight lighting circuit
• d.a low battery or high resistance in the starter circuit✓

The solenoid clicks but cannot pull enough current to spin the motor when the battery is weak or the cables and connections have high resistance, and the lights dim under the attempted load. A voltage-drop test of the cables isolates the fault. Clean, tight connections and a good battery are essential.

Inside an alternator, the component that converts the stator's alternating current into the direct current the vehicle uses is the:

• a.slip-ring brushes that feed current to the spinning rotor
• b.voltage regulator that maintains the system's charging voltage
• c.diode rectifier assembly✓
• d.drive pulley that is turned by the accessory drive belt

The diode rectifier bridge changes the three-phase AC produced in the stator into DC for the battery and loads. A shorted or open diode causes low output and AC ripple. The regulator, by contrast, controls output voltage by varying field current.

The voltage regulator in a charging system controls output by adjusting the:

• a.speed at which the alternator's drive pulley is being turned
• b.field (rotor) current supplied to the alternator✓
• c.number of rectifier diodes that are conducting at any one time
• d.resistance present in the battery cables and their connections

The regulator maintains system voltage, typically near 13.5 to 14.5 volts, by varying the field current in the rotor, which changes the magnetic field strength. More field current raises output; less lowers it. Many modern regulators are integrated and PCM-controlled.

An undercharging condition (battery repeatedly low) can be caused by all of the following EXCEPT:

• a.a voltage regulator that is holding output voltage too high✓
• b.a loose or glazed alternator drive belt that is slipping badly
• c.a failed rectifier diode that is reducing the alternator's output
• d.high resistance in the charging circuit wiring and connections

Undercharging comes from anything that limits output: a slipping belt, high-resistance connections, or failed diodes. A regulator holding voltage too high causes overcharging, not undercharging. A charging-system test with voltage-drop checks isolates the cause.

An overcharging condition that boils the battery and shortens its life is most often caused by:

• a.a completely open charging circuit with no current flowing at all
• b.a voltage regulator allowing excessive charging voltage✓
• c.a fully discharged battery that is drawing a large charging current
• d.a slipping alternator drive belt that cannot spin the rotor fast enough

A regulator that fails to limit voltage lets the alternator push charging voltage too high, overheating and gassing the battery. Symptoms include a swollen case, corrosion, and frequent water loss on serviceable batteries. Measuring charging voltage confirms the fault.

Technician A says a slipping or worn serpentine belt can reduce alternator output and cause undercharging. Technician B says a seized belt tensioner can also affect charging system performance. Who is correct?

• a.Both A and B✓
• b.Technician A only
• c.Technician B only
• d.Neither A nor B

A belt that slips cannot spin the alternator fast enough for full output, and a seized or weak tensioner lets the belt slip as well. Both technicians are correct. Belt condition and tensioner operation should be inspected during a charging complaint.

A good engine-to-body ground strap is important because:

• a.it carries the ignition secondary voltage over to the spark plugs
• b.it supplies the primary charging voltage back to the vehicle battery
• c.it electrically insulates the engine away from the vehicle frame
• d.it provides a low-resistance return path for many electrical loads✓

The ground strap completes circuits back to the battery negative; a corroded or broken strap forces current through unintended paths, causing dim lights, erratic gauges, or hard starting. Voltage-drop testing the ground finds excessive resistance. Clean, tight ground connections are essential.

When performing a voltage-drop test on the ground side of a starter circuit, a reading much higher than a few tenths of a volt indicates:

• a.excessive resistance in the ground path✓
• b.too much current being made available by the vehicle's battery
• c.a perfectly clean, low-resistance connection with almost no drop
• d.a short to power somewhere else in the same starter circuit

Voltage drop measures the voltage lost across a connection under load; a high drop on the ground side reveals corrosion or a loose connection adding resistance. The test is done with the circuit operating. Cleaning and tightening the ground reduces the drop.

Replacing incandescent bulbs with LED bulbs in a turn-signal circuit can cause the flasher to blink too fast because LEDs:

• a.draw far more current than the original incandescent bulbs did
• b.increase the resistance of only the ground side of the circuit
• c.draw much less current than the original bulbs✓
• d.produce alternating current within the turn-signal circuit

Thermal and many electronic flashers rely on the current an incandescent bulb draws; an LED's low draw can be read as a bulb-out condition, causing rapid flashing. A load resistor or an LED-compatible flasher corrects it. This mimics the fast-flash warning of a burned-out bulb.

A dual-filament bulb, such as a combined tail and brake light, uses two filaments so that:

• a.it can double the system voltage that is delivered at the socket
• b.one filament gives dim running light and the other bright brake light✓
• c.it removes any need for a separate ground connection at the socket
• d.it can operate on alternating current supplied only to the socket

A dual-filament bulb has a low-intensity filament for the tail/running light and a brighter filament for the brake or turn function, each on its own circuit. A shared ground and correct socket indexing are required. A bad ground can cause feedback between the two circuits.

A turn-signal indicator that flashes noticeably faster than normal on one side usually indicates:

• a.a fully charged battery and a healthy charging system
• b.excessive alternator output overcharging the whole system
• c.a shorted or stuck brake light switch feeding the circuit
• d.a burned-out bulb on that side✓

Many flasher systems speed up when one turn-signal bulb burns out because total current drops, signaling the fault to the driver. Replacing the failed bulb restores the normal flash rate. A poor socket ground can mimic the symptom.

On a vehicle with a body control module (BCM) and multiplexed wiring, many accessories are operated by:

• a.data messages sent over a communication bus rather than separate wires✓
• b.mechanical linkages that run from the dashboard switches to each load
• c.a single large fuse that feeds every accessory in the vehicle directly
• d.the alternator field circuit, which is used exclusively for accessories

Multiplexing lets modules share information over a data bus (such as CAN), so a switch sends a message and the module powers the load, reducing wiring. Diagnosis requires a scan tool to read module data and network status. A bus fault can affect several unrelated functions at once.

A CAN (controller area network) bus in a modern vehicle is best described as:

• a.a two-wire network that lets control modules share data✓
• b.the ground strap that connects the engine block to the body
• c.a network of vacuum lines used to operate the emissions controls
• d.a heavy high-current cable that powers the engine's starter motor

The CAN bus uses a twisted pair (CAN High and CAN Low) so modules exchange data messages for coordinated operation. Correct termination resistance, typically 60 ohms across the pair, is needed for communication. Bus faults can disable communication and set network codes.

A parasitic (key-off) current draw is generally considered excessive when it exceeds roughly:

• a.50 milliamps after the modules have gone to sleep✓
• b.a value as high as the alternator's maximum rated output current
• c.about 5 amps flowing continuously with the ignition key turned off
• d.a value equal to the battery's full cold cranking amps rating

Most vehicles settle to about 50 milliamps or less once modules power down; more than that will discharge the battery over time. The technician waits for modules to sleep, then measures in series or with a low-current clamp. Pulling fuses one at a time isolates the circuit.

When replacing a blown fuse, the technician should install a fuse of the:

• a.lowest amperage rating that happens to be available in the shop
• b.next higher amperage rating so that it will not blow again soon
• c.same amperage rating as specified for that circuit✓
• d.any rating on hand, since the fuse value does not really matter

A fuse is sized to protect its wiring, so a replacement must match the specified rating; a higher-rated fuse can let the wire overheat and start a fire. A repeatedly blown fuse signals a fault to repair, not a fuse to upsize. Always correct the underlying overload or short.

In American Wire Gauge (AWG), a wire with a smaller gauge number:

• a.has more resistance per foot than a larger gauge number
• b.is physically larger and carries more current✓
• c.is physically smaller in diameter and carries less current
• d.is suitable only for ground connections and nothing else

In AWG, the numbering is inverse: a smaller number means a larger-diameter conductor with lower resistance and higher current capacity. Choosing adequate wire size for the load and length prevents voltage drop and overheating. Battery cables use very low gauge numbers.

The preferred method for a reliable, permanent automotive wire repair is generally to:

• a.solder or use a proper crimp connector, then seal the joint✓
• b.twist the bare wires together and wrap them with electrical tape only
• c.splice by pressing metal staples through the wire's insulation
• d.join the connection together using a common household wire nut

A soldered or properly crimped connection sealed with adhesive-lined heat shrink resists corrosion and vibration for a durable repair. Twisting and taping or using wire nuts is unreliable in a vehicle's environment. Manufacturer procedures may specify crimp-and-seal for certain circuits.

On a standard ISO relay, terminals 85 and 86 connect to the:

• a.control coil that creates the magnetic field✓
• b.chassis ground bus that the relay case connects to
• c.heavy high-current load contacts inside the relay body
• d.battery positive feed terminal on the relay only

Terminals 85 and 86 energize the relay's coil, while 30 and 87 (and 87a) carry the switched high-current load. Energizing the coil moves the contacts to power the load. Knowing this layout lets a technician bench-test or bypass a relay safely.

A fuel-gauge sending unit in the tank typically signals fuel level to the gauge using a float connected to a:

• a.thermistor that senses the temperature of the fuel in the tank
• b.small internal alternator that generates voltage with the level
• c.pressure switch that simply opens when the tank runs empty
• d.variable resistor (rheostat) whose resistance changes with level✓

The float moves a wiper along a resistor, changing resistance as the level rises or falls, and the gauge or module reads that as fuel level. A worn resistor card can cause erratic or stuck readings. Modern systems may process the signal through a module.

An oil-pressure warning lamp is usually operated by a switch that:

• a.opens the charging circuit whenever the oil pressure drops
• b.produces its own signal voltage internally from the engine oil pump
• c.measures the engine coolant temperature rather than oil pressure
• d.closes to ground and lights the lamp when oil pressure is low✓

A simple oil-pressure warning switch grounds the lamp circuit when pressure is below its threshold, turning the light on. Rising oil pressure opens the switch and the lamp goes out. A gauge-type sender instead varies resistance to move a pointer.

A door-operated dome (courtesy) light most commonly turns on when the door switch:

• a.increases the electrical resistance of the lamp's bulb
• b.provides a path to ground for the lamp circuit✓
• c.disconnects the courtesy lamp entirely from its fuse feed
• d.sends charging voltage from the alternator to the battery

Many courtesy lamps are always supplied with power and light when the door jamb switch completes the ground path as the door opens. A stuck or corroded switch can leave the light on and drain the battery. Body modules now often control this timing.

A blower motor that runs only on high speed but not on lower speeds most likely has a fault in the:

• a.alternator diode rectifier bridge inside the charging system
• b.blower motor resistor (or its control module)✓
• c.blower motor itself, which has failed and is now completely dead
• d.battery, which cannot supply enough current for the low speeds

Lower fan speeds pass current through a resistor pack (or solid-state control); high speed usually bypasses it, so if only high works, the resistor or its circuit is open. The motor itself is proven good because high speed operates. Corrosion at the resistor connector is a common cause.

Technician A says a digital multimeter's min/max feature can help catch an intermittent voltage glitch. Technician B says a graphing meter or scope shows signal changes over time better than a numeric display. Who is correct?

• a.Both A and B✓
• b.Technician B only
• c.Technician A only
• d.Neither A nor B

Min/max recording captures brief highs and lows a technician might miss while watching, and a graphing meter or oscilloscope displays the waveform to reveal dropouts and noise. Both technicians are correct. Choosing the right tool speeds intermittent-fault diagnosis.

Corroded or loose battery terminals commonly cause which symptom?

• a.a steady, abnormally high engine idle speed when warm
• b.overcharging of an otherwise healthy and fully charged battery
• c.excessive alternator output voltage at highway cruising speed
• d.slow or no cranking and intermittent electrical problems✓

Resistance at the terminals limits current to the starter and other loads, causing slow cranking, no-starts, or flickering electronics. Cleaning the posts and clamps and tightening them restores a solid connection. A voltage-drop test confirms terminal resistance.

On a hybrid or electric vehicle, cables and components colored bright orange indicate:

• a.low-voltage accessory wiring that is completely safe to touch
• b.the vehicle's chassis and body ground connection points
• c.high-voltage circuits that require special safety precautions✓
• d.standard 12-volt starter and main battery cables

Orange insulation and connectors mark the high-voltage system, which can be lethal; technicians must follow de-energizing procedures and use insulated tools and gloves. Never cut or probe orange cabling without proper training. Service information specifies the shutdown steps.

A relay is often used instead of running full load current through a dashboard switch because it:

• a.increases the total system voltage that is available to the load
• b.lets a small switch current control a much larger load current✓
• c.converts the vehicle's direct current into alternating current
• d.removes any need for a protective fuse in the load circuit

A relay uses a low-current control circuit to close heavy-duty contacts, so the dash switch and its wiring stay small and cool while the relay handles the high current. This protects switches and reduces voltage drop to the load. Headlights, fuel pumps, and fans commonly use relays.

A short to power (a wire touching a constant hot source) differs from a short to ground because a short to power will:

• a.stop all current flow throughout the entire vehicle at once
• b.cause a load to operate when it should be off✓
• c.always blow the circuit's protective fuse almost immediately
• d.occur only inside the alternator's internal rectifier bridge

A short to power feeds voltage into a circuit that should be off, so a lamp or motor may run unexpectedly, whereas a short to ground usually blows a fuse. Backprobing and isolating sections of the harness helps locate it. Wiring diagrams show where an accidental power feed could originate.

A wheel-related speed signal used by the speedometer and other systems is often produced by a:

• a.hydrometer that measures the movement of fluid in the axle
• b.sensor that generates a signal as a toothed ring passes it✓
• c.potentiometer that is turned directly by the steering wheel
• d.thermistor that changes its resistance as the vehicle speed changes

Vehicle and wheel speed sensors typically use a magnetic or Hall-effect pickup that produces pulses as a toothed reluctor or tone ring rotates. The module converts pulse frequency into speed. A damaged tone ring or sensor causes speed-signal faults and can affect ABS and the speedometer.

A test light is useful for quick checks but is less desirable than a digital multimeter for some tests because a test light:

• a.draws no current at all from the circuit that is being tested
• b.reads circuit resistance more accurately than a meter does
• c.is the required tool for measuring electrolyte specific gravity
• d.cannot measure exact voltage and may load sensitive circuits✓

A test light only shows presence of voltage and can draw enough current to damage low-power electronic circuits, while a DVOM gives precise measurements with very high input impedance. Use a high-impedance meter on computer and sensor circuits. The test light still has value for quick power/ground checks on robust circuits.

A component that stores an electrical charge and is often used to reduce voltage spikes or noise is a:

• a.thermistor, which changes its resistance as temperature changes
• b.relay coil, which creates a magnetic field when it is energized
• c.capacitor✓
• d.diode, which instead allows current to flow in only one direction

A capacitor stores charge and can smooth voltage or absorb spikes, such as suppressing radio noise or stabilizing a circuit. A diode, by contrast, allows current one way, and a thermistor changes resistance with temperature. Capacitors are common in filtering and timing applications.

If two 12-volt loads are wired in parallel across the battery, the total current drawn from the battery is:

• a.zero, because the two branch currents cancel each other out
• b.always less than the current drawn by either load alone
• c.the sum of the currents drawn by each load✓
• d.the same as the current drawn by just one load by itself

Because parallel branches each draw their own current at full source voltage, the battery must supply the sum of both branch currents. Adding parallel loads therefore increases total draw and can overload a shared fuse. This is why circuit and fuse capacity must match the combined load.

A gauge that reads inaccurately high or erratically may be traced to a poor ground because:

• a.the gauge internally generates its own reference voltage
• b.a bad ground supplies extra reference voltage into the gauge circuit
• c.a grounding condition has no effect at all on gauge accuracy
• d.added ground resistance changes the current the gauge sees✓

Many gauges depend on a stable ground reference; extra resistance in the ground path shifts the circuit values and skews the reading. Cleaning and tightening the instrument-cluster or sensor ground often corrects erratic gauges. Voltage-drop testing the ground confirms the fault.

A vehicle's electrical loads such as headlights, radio, and blower are wired in parallel rather than series so that:

• a.each load receives full system voltage and works independently✓
• b.the source voltage is divided into small shares among the loads
• c.turning off any one load would shut off all the other loads too
• d.all of the loads must always be switched on together at once

Parallel wiring puts each accessory directly across the battery, so every load gets full voltage and one can operate or fail without affecting the others. Series wiring would divide voltage and make the loads dependent on one another. This is why most vehicle circuits are parallel.

A vernier or dial caliper is commonly used to measure:

• a.inside, outside, and depth dimensions to about a thousandth of an inch✓
• b.the electrical resistance measured across a wiring connector
• c.the amount of torque that has been applied to a fastener
• d.only the outside diameter of round shafts and nothing else

A caliper measures outside, inside, and depth dimensions and reads to roughly 0.001 inch (or 0.02 mm), making it versatile for many measurements. It is less precise than an outside micrometer for critical diameters. Proper technique avoids rocking the jaws for an accurate reading.

A thread pitch gauge is used to determine a fastener's:

• a.overall length measured under the head of the fastener
• b.torque-to-yield final tightening specification
• c.hardness or strength grade of the fastener's steel
• d.number of threads per inch or thread pitch✓

A thread pitch gauge has blades matching common thread counts; the blade that fits the threads identifies the pitch or threads per inch. This helps select the correct nut, bolt, or tap. Matching pitch prevents cross-threading and stripped fasteners.

Converting torque units, 1 foot-pound is equal to:

• a.1.36 inch-pounds, mixing up newton-meters with inches
• b.100 inch-pounds, confusing feet with a larger unit
• c.12 inch-pounds✓
• d.10 inch-pounds, using a rounded conversion factor

Because a foot is 12 inches, one foot-pound equals 12 inch-pounds of torque. A specification of 60 inch-pounds is therefore 5 foot-pounds. Using the correct unit prevents badly over- or under-tightened fasteners on small components.

A common and recommended practice for a click-type torque wrench is to:

• a.store it fully tightened in order to keep it accurate
• b.back the setting down to its lowest value for storage✓
• c.use it as a breaker bar to loosen tight, seized fasteners
• d.leave it set at its maximum torque value between uses

Relaxing the spring by dialing the wrench down to its lowest setting for storage helps preserve calibration. A torque wrench should not be used to loosen fasteners or as a breaker bar, which can damage it. Periodic recalibration keeps readings accurate.

On an SAE bolt head, radial lines (slashes) stamped on the head indicate the:

• a.country in which the fastener was manufactured
• b.overall length of the bolt shank beneath the head
• c.thread pitch, or threads per inch, of the bolt
• d.strength grade of the fastener✓

SAE bolt grades are marked with radial lines; a grade 5 bolt has three lines and a grade 8 has six, indicating higher strength. Metric bolts use a numeric class such as 8.8 or 10.9. Replacing a bolt with a lower grade than specified can cause failure.

A thread-repair insert (such as a Heli-Coil) is used to:

• a.increase a bolt's outside diameter permanently in the part
• b.restore stripped internal threads to the original size✓
• c.measure the depth of a drilled or tapped bolt hole
• d.harden a soft fastener after it has been installed

A coil or solid insert is installed into a re-tapped hole to rebuild damaged internal threads back to the original bolt size, avoiding replacement of the whole part. It is common in aluminum components like cylinder heads. Correct drill, tap, and insert length must be used.

The correct type of fire extinguisher for a gasoline or oil (flammable liquid) fire is a class:

• a.K extinguisher
• b.D extinguisher
• c.B extinguisher✓
• d.A extinguisher

Class B extinguishers are rated for flammable liquids like gasoline and oil, while class A is for ordinary combustibles and class C for energized electrical fires. Many shop extinguishers are rated B and C together. Using the wrong type can spread a liquid fire.

A Safety Data Sheet (SDS) provides a technician with information about:

• a.the wiring diagram and pin-out for a specific vehicle circuit
• b.the alignment angles such as camber and toe for the suspension
• c.the torque specifications for tightening the engine's fasteners
• d.the hazards, handling, and first aid for a chemical product✓

An SDS details a product's hazards, safe handling, protective equipment, and emergency and first-aid measures. Employers must keep these accessible for shop chemicals. Reading the SDS before use protects the technician and coworkers.

Running an engine indoors requires connecting the exhaust to a ventilation system primarily because:

• a.it prevents the vehicle's battery from being overcharged
• b.exhaust contains carbon monoxide, a colorless, odorless, deadly gas✓
• c.venting improves the accuracy of the wheel alignment machine
• d.the exhaust would otherwise cool the engine down far too quickly

Carbon monoxide in exhaust is toxic and cannot be seen or smelled, so an exhaust extraction system must vent it outside. Even brief exposure in an enclosed shop is dangerous. Ventilation is a basic and required shop safety practice.

Before working around a deployed-capable airbag (SRS) system, the technician should generally:

• a.carry a live airbag module face-down and pointed toward the body
• b.leave the battery connected so the system keeps full power
• c.strike the airbag module firmly to test that it still responds
• d.disconnect the battery and wait the specified time before servicing✓

Disconnecting the battery and waiting the manufacturer-specified time lets the SRS capacitor discharge so the airbag cannot deploy accidentally during service. A live module should be carried facing away from the body and set face-up. Always follow the service manual's SRS precautions.

When lifting a heavy object such as a transmission by hand, a technician should:

• a.hold the load out far away from the body while lifting
• b.lift with the legs while keeping the back straight✓
• c.bend at the waist and lift using the muscles of the back
• d.twist the torso to one side while raising the heavy load

Lifting with the leg muscles and a straight back, keeping the load close, reduces the risk of back injury. Bending and twisting at the waist strains the spine. For very heavy items, a hoist or a coworker's help should be used.

An impact wrench should generally NOT be used for final tightening of wheel lug nuts because it:

• a.cannot loosen rusted or seized lug nuts on the wheel at all
• b.turns the fasteners too slowly to seat the wheel properly
• c.produces no useful rotational force on the lug nuts
• d.can over-torque the fasteners and warp brake rotors✓

An impact wrench can apply uneven, excessive torque that stretches studs and distorts rotors, so lug nuts should be final-tightened with a torque wrench in a star pattern. Torque sticks help limit force but are not a substitute for verifying with a torque wrench. Proper torque prevents warping and loosening.

A left-hand thread fastener is designed so that it:

• a.uses a much finer thread pitch than a right-hand thread
• b.loosens when turned clockwise and tightens counterclockwise✓
• c.requires no torque specification at all when it is tightened
• d.cannot ever be removed once it has been installed

Left-hand threads reverse the normal direction, tightening counterclockwise, and are used where normal rotation would tend to loosen a fastener, such as some spindle nuts or blade bolts. Recognizing them prevents damage from forcing them the wrong way. They are often marked with an 'L' or grooves.

A bench grinder's tool rest should be adjusted so the gap between the rest and the wheel is:

• a.small, about one-sixteenth of an inch, to keep work from being pulled in✓
• b.exactly one full inch, which is considered the safe distance
• c.as large as possible in order to give plenty of clearance
• d.irrelevant, because the gap does not affect safe operation

Keeping the tool rest within about 1/16 inch of the wheel prevents the workpiece from catching and being drawn between the rest and the wheel. Eye protection and inspecting the wheel for cracks are also essential. Never grind on the side of a straight wheel.

A castle (castellated) nut is used with a cotter pin to:

• a.positively lock the nut so it cannot back off✓
• b.increase the clamping torque well beyond the specification
• c.measure the amount of endplay present in the assembly
• d.seal fluid inside a threaded fitting to prevent a leak

The slots in a castle nut align with a hole in the fastener so a cotter pin holds the nut from rotating loose, common on tie-rod ends and spindle nuts. A new cotter pin should be used on reassembly. This is a mechanical locking method for safety-critical fasteners.

The vehicle identification number (VIN) is important to a technician because it:

• a.lists the previous owner's name and contact details
• b.shows the current amount of fuel remaining in the tank
• c.identifies the exact vehicle for correct parts and service info✓
• d.records only the vehicle's tire-pressure specification

The 17-character VIN encodes the make, model, engine, and other build details needed to look up the right parts, specifications, and procedures. It is found on the dash, door jamb, and registration. Ordering parts by VIN avoids costly mismatches.

A technical service bulletin (TSB) issued by a manufacturer provides:

• a.guidance and updated procedures for known, recurring problems✓
• b.the vehicle's original window-sticker selling price
• c.a specific customer's personal maintenance history
• d.a legally mandated safety recall notice sent to the owner

A TSB documents a known issue and the recommended repair or updated procedure to help technicians fix recurring problems efficiently. Unlike a recall, a TSB is not a mandatory safety campaign. Checking TSBs early can save diagnostic time.

Penetrating oil is applied to a rusted, seized fastener in order to:

• a.measure how deep the corrosion has gone into the metal
• b.weld the fastener permanently into place in the threads
• c.seep into the threads and ease removal✓
• d.increase the torque rating that the fastener can withstand

Penetrating oil works into corroded threads to reduce friction so a stuck fastener can be loosened with less risk of breaking it. Allowing it time to soak improves results. Heat may also be used carefully to help free badly seized fasteners.

A dial or digital micrometer typically offers greater precision than a caliper, reading to about:

• a.one full centimeter
• b.one ten-thousandth of an inch on some models✓
• c.one full inch, far coarser than any precision tool would give
• d.one-eighth of an inch

A micrometer measures to 0.001 inch, and vernier or digital versions resolve to 0.0001 inch, making it the tool for critical diameters like crankshaft journals. A caliper, by contrast, reads to about 0.001 inch. Proper feel and calibration ensure an accurate micrometer reading.

When jacking up a vehicle, the technician must place the jack and stands at:

• a.the manufacturer's designated lift points✓
• b.the plastic bumper covers at the front or the rear
• c.any flat spot found on the vehicle's sheet-metal floor pan
• d.the middle section of the exhaust pipe under the vehicle

Factory lift points are reinforced to bear the vehicle's weight safely; jacking on unapproved spots can crush panels or cause the vehicle to fall. Rated jack stands must support the vehicle before anyone works underneath. The service manual shows the correct locations.

A dial bore gauge is used to measure:

• a.the outside diameter of a crankshaft main or rod journal
• b.the inside diameter, taper, and out-of-round of a cylinder bore✓
• c.the amount of torque that has been applied to a head bolt
• d.the electrical resistance of a sensor's signal circuit

A dial bore gauge measures internal diameter accurately at several depths, revealing taper and out-of-round in cylinders or bores. It must be set to size with a micrometer or ring first. Readings guide the decision to bore or hone a cylinder.

Compressed air used for cleaning should be handled carefully because:

• a.it improves a person's eyesight when it is aimed at the face
• b.it is completely harmless to a person at any pressure level
• c.it must be inhaled in order to check the air's quality
• d.high-pressure air can inject debris into skin or eyes and injure✓

High-pressure air can drive dirt and particles into the skin or eyes and should never be aimed at oneself or others; eye protection is required. Regulators limit pressure for cleaning tasks. Following shop safety rules prevents serious injury.

Used engine oil, coolant, and similar fluids must be:

• a.dumped onto the bare ground behind the repair shop
• b.poured directly down the shop floor drain to get rid of it
• c.collected and disposed of or recycled according to regulations✓
• d.mixed together and then burned off out in the open air

Waste automotive fluids are regulated and must be captured and sent for proper recycling or disposal to protect the environment and comply with law. Mixing incompatible fluids can prevent recycling. Shops keep labeled containers for each waste type.

Recovering and recycling A/C refrigerant during service is required because:

• a.refrigerant is completely safe to release once the engine is off
• b.recovery is done in order to lower the vehicle's tire pressure
• c.it is only a manufacturer suggestion rather than a legal rule
• d.venting refrigerant to the atmosphere is illegal and harmful✓

Refrigerant must be recovered with proper equipment rather than vented, both to comply with environmental law and to protect the atmosphere. Technicians handling refrigerant require the appropriate certification. Recovered refrigerant can be recycled and reused.

Standard shop practice for starting fasteners on a critical assembly is to:

• a.use maximum impact-gun power to seat them all as quickly as possible
• b.tighten only the outer fasteners and skip the center ones
• c.start all fasteners by hand before final tightening to avoid cross-threading✓
• d.run each fastener straight to full torque one at a time immediately

Starting threads by hand ensures they engage correctly and are not cross-threaded before power tools or final torque are applied. Many assemblies are then torqued in a specified sequence and multiple steps. This prevents leaks, distortion, and stripped threads.