Circuit Description and Diagnostic Chart

SYSTEM: 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 engine control module (ECM) operated only the IAC valve to perform idle-up and provide feedback for the target idling speed, a VSV for idle-up control is also added (for air conditioning).

WIRING DIAGRAM





DIAGNOSTIC PROCEDURE
1. Check voltage terminals ISCO, ISCC.
^ If OK check and replace the engine control module.
^ If not OK proceed to step 2.
2. Check operation of the IAC valve.
^ If OK proceed to step 3.
^ If not OK repair or replace the IAC valve.
3. Check for open and short in harness and connector between R/B No.2 and IAC valve, IAC valve and ECM.
^ If OK Check for ECM power source circuit
^ If not OK Repair or replace harness or connector.