Idle Air Control (IAC) Valve Circuit

IDLE AIR CONTROL (IAC) VALVE CIRCUIT

Circuit Description




The rotary solenoid type IAC valve is provided on the intake air chamber and intake air bypassing the throttle valve is directed to the IAC valve through a passage.

In this way the intake air volume bypassing the throttle valve is regulated, controlling the engine speed.

The ECM operated only the IAC valve to perform idle-up and provide feedback for the target idling speed, but in the 4A-FE engine of the Corolla, a VSV for idle-up control is also added (for air conditioning).




Diagnostic Chart




Wiring Diagram

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Inspection Procedure