Idle Air Control Valve Circuit

CIRCUIT DESCRIPTION
The 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.
A step motor is built into the IAC valve. It consists of 4 coils, a magnetic rotor, valve shaft and valve. When current flows to the coils due to signals from the ECM, the rotor turns and moves the valve shaft forward or backward, changing the clearance between the valve and the valve seat.
In this way the intake air volume bypassing the throttle valve is regulated, controlling the engine speed. There are 125 possible positions to which the valve can be opened.








Reference INSPECTION USING OSCILLOSCOPE:
- With engine idling measure waveforms between terminals ISC1, ISC2, ISC3, ISC4 and ED1 of engine control module when A/C switch ON or OFF.

HINT: The correct waveform appears as shown in the above images.





DIAGNOSTIC CHART





WIRING DIAGRAM








INSPECTION PROCEDURE