A GM vehicle with high idle speed is being diagnosed. Technician A says if the IAC counts show a value of 0, a vacuum leak is a possible cause. Technician B says if the IAC counts show a value of 0, the ECM may not be able to control the IAC. Who is correct?
A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question

Quizplus · Accepted Answer

Both technicians are correct. Technician A is correct in stating that a vacuum leak could cause the IAC (Idle Air Control) counts to show a value of 0 because the engine might be getting additional air from the leak, reducing the need for the IAC to let in more air. Technician B is correct in stating that if the IAC counts show a value of 0, it could indicate that the ECM (Engine Control Module) is unable to control the IAC, possibly due to a malfunction in the IAC or in the ECM's control circuit.

A GM Vehicle with High Idle Speed Is Being Diagnosed