ASE Automobile (A1–A8)

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

1. AIgnition timing advance
2. BEngine oil level
3. CThe air-fuel ratio (rich or lean)Đúng
4. DCoolant temperature

Vì sao: 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.

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

1. A3 ampsĐúng
2. B16 amps
3. C0.33 amps
4. D48 amps

Vì sao: 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.