Engine Performance (A8)Câu 99 / 120
A P0420 code (catalyst efficiency below threshold) most often indicates:
a.A degraded catalytic converter or an O2 sensor issue
b.A slipping transmission
c.A worn wheel bearing
d.A faulty ABS sensor
Giải thích
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.
Luyện miễn phí toàn bộ 120 câu hỏi — không cần đăng ký.
Câu hỏi liên quan cùng chủ đề
- 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?
- 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?
- 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?
- In a modern coil-on-plug ignition system, each coil:
- A knock sensor allows the PCM to:
- The EVAP system is designed to:
Cập nhật gần nhất: · quy trình kiểm tra
Đội Ngũ Biên Tập PrepPass · Đối chiếu với ASE Automobile Certification Series (A1–A8) · Quy trình kiểm tra