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. PCM monitors IAC circuit for low and high voltage faults.

DTC will set when either IAC valve coil "A" or "B" is commanded on and off and voltage on one side of coil circuit is low (grounded) when ignition voltage should be high (ignition voltage). A short to ground will also set this DTC when PCM is commanding IAC valve to move. This diagnostic runs continuously when engine is running and PCM is commanding IAC valve to move.