While discussing the catalyst efficiency monitor: Technician A says if a fault occurs in the catalyst monitor system on three drive cycles, the MIL is illuminated. Technician B says if the catalytic converter is not reducing emissions properly, the voltage frequency increases on the upstream HO₂S. Who is correct? A) A only B) B only C) both A and B D) neither A nor B

Question

Quizplus · Accepted Answer

Technician A is correct because if a fault is detected in the catalyst monitor system across multiple drive cycles (typically three), the Malfunction Indicator Lamp (MIL) will illuminate to alert the driver of an issue. Technician B's statement is incorrect because the voltage frequency change related to emissions reduction efficiency is typically observed in the downstream oxygen sensor, not the upstream sensor. The upstream sensor's voltage fluctuates based on the oxygen content in the exhaust before it passes through the catalytic converter, primarily to adjust the air-fuel mixture, not to monitor the efficiency of the catalytic converter.

While Discussing the Catalyst Efficiency Monitor: Technician a Says If