Circuit Description

The Idle Air Control (IAC) valve is controlled by the PCM. PCM uses the IAC to maintain a desired idle speed, which can vary depending on input to PCM and other criteria. If PCM detects that idle speed is out of IAC systems range of control at idle, it will perform an active test while the vehicle is being driven.

During this test, PCM will command the IAC valve to move while monitoring MAF. If the expected change in MAF is detected, and IAC operation is verified, but since idle RPM was out of IAC system control and IAC valve is working, DTC P0507 will set. DTC P1509 will set, when there is no change in MAF, and IAC valve is not functioning and idle RPM is out of IAC system control.