Description and Diagnosis Procedure

SYSTEM: IAC Valve Circuit

CIRCUIT DESCRIPTION



The rotary solenoid type idle air control (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 operates the IAC Valve only to perform idle-up and provide feedback for the target idling speed, a vacuum switching valve for idle-up control is also added (for air conditioning).

DIAGNOSTIC PROCEDURE
1. CHECK VOLTAGE TERMINALS ISCO, ISCC.
- If not OK proceed to step 2.
- If OK check and replace ECM.
2. CHECK OPERATION OF THE IAC VALVE.
- If OK proceed to step 3.
- If not OK replace IAC valve.
3. CHECK FOR OPEN AND SHORT IN HARNESS AND CONNECTOR BETWEEN J/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.