Idle Air Control (IAC) Valve

The idle air control (IAC) valve is attached to the underside of the throttle body. The powertrain control module (PCM) uses the IAC valve in order to control engine idle speed. The PCM controls the IAC valve by varying the ON time of a repeating ON/OFF signal (duty cycle). A magnet inside the IAC valve operates a rotary valve that controls the opening of the idle air (bypass) passage in the throttle body. The idle air passage allows air to enter the engine without passing over the throttle valve. The strength of the magnet in the throttle body is concurrent with the current flow in the IAC circuit.

The IAC valve contains an engine coolant passage that enables the IAC valve to operate more efficiently at cold temperatures. The IAC valve enables the PCM to easily control engine idle speed by precisely metering the engine's air intake at closed throttle.