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 will set when actual engine speed is less than 100 RPM or greater of desired RPM and ECT is greater than 140°F (60°C). This diagnostic runs continuously every 17 seconds when these conditions have been met.