Circuit Description

The Idle Air Control (IAC) valve consists of a 2 coil stepper motor controlling a pintle. PCM pulses a signal to the IAC valve by switching the high and low side circuits, depending on which direction the pintle needs to move. The amount of movement being commanded is displayed in counts on scan tool. With engine off, IAC pintle is retracted (80-100 counts) allowing maximum air during a restart. After start-up, the motor position commanded is based on coolant temperature and TP sensor values.

DTC P0506 (Idle RPM Too Low) will set when RPM is too low and PCM has commanded the IAC valve open and the actual RPM is greater than 100-300 RPM of the desired RPM. Amount of RPM error allowed depends on ECT.

DTC P1508 (IAC Valve Closed) may set along with P0506 if the intrusive test indicates that the valve is stuck in an open position.

DTC P1509 (IAC Valve Open) may set along with P0507 is the intrusive test indicates that the valve is stuck in a closed position.

IAC is continuously checked with engine is running and PCM in idle control.