Engine operating modes are being discussed. Technician A says that when the engine is in closed-loop mode, the PCM monitors sensor inputs, then adjusts the timing, air fuel ratio, and emission controls. Technician B says the system will switch into open loop when the throttle is fully opened or the oxygen sensors cool down during idle. Who is correct?
A)A only
B)B only
C)both A and B
D)neither A nor B

Question

Quizplus · Accepted Answer

Both technicians are correct. In closed-loop mode, the PCM indeed monitors sensor inputs to adjust timing, air-fuel ratio, and emission controls as stated by Technician A. Technician B is also correct in stating that the system switches to open loop when the throttle is fully opened or when the oxygen sensors cool down during idle, as these conditions necessitate a departure from the feedback-controlled adjustments of closed-loop operation.

Engine Operating Modes Are Being Discussed