Ces Test Questions And Answers For Engine Management Link

A vacuum leak adds unmetered air, causing the O2 sensor to see lean exhaust. The PCM adds fuel (positive LTFT). At idle, vacuum is high, so the leak affects mixture most; at higher RPM, manifold vacuum drops, so the leak’s effect lessens, reducing LTFT. A high MAF reading at idle (3.2 vs 2.5 g/s) indicates extra airflow the PCM cannot account for, confirming an unmetered air leak. A weak pump or clogged filter would affect all RPMs more evenly; restricted exhaust would cause negative trim or power loss. Question 2 – Ignition and Misfire Detection Question: A technician observes a P0302 (Cylinder 2 misfire) on a coil-on-plug engine. The misfire counter shows misfires only under load. A swapped coil with cylinder 4 moves the misfire to cylinder 4. What is the repair?

A properly functioning catalytic converter stores oxygen, causing the downstream O2 sensor to remain relatively steady around 0.45–0.7V. However, if the upstream sensor is switching slowly (should switch 1–3 times per second at 2500 RPM), it indicates a slow sensor or a fuel control issue. But the clue here is high NOx combined with a steady downstream 0.7V – a steady 0.7V suggests a rich bias, but NOx is formed under lean/hot conditions. More importantly, a failed converter cannot store oxygen, so the downstream sensor mimics the upstream. However, in this case, the downstream is steady – that actually suggests the converter is working. Wait – reanalysis: The downstream should be steady if converter works. But NOx high means converter not reducing NOx – possibly thermal degradation or contamination. The upstream slow switching means O2 sensor lazy, causing improper mixture control and overheating converter. Correct answer is B – aging O2 sensor causing false lean/rich cycles leading to high NOx. ces test questions and answers for engine management

C) Replace ignition coil cylinder 2

B) Vacuum leak

A) Replace spark plug cylinder 2 B) Replace fuel injector cylinder 2 C) Replace ignition coil cylinder 2 D) Perform compression test cylinder 2 A vacuum leak adds unmetered air, causing the

A) Failed catalytic converter