P0505

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 hose. A step motor is built into the IAC valve. It consists of four coils,the magnetic rotor, valve shaft and valve. When current flows to the coils due to signals from the Engine Control Module (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.






INSPECTION USING OSCILLOSCOPE
With the engine idling measure between terminals ISC1, ISC2, ISC3, ISC4 and EO1 of ECM when A/C switch ON or OFF.
HINT: The correct waveforms are as shown.





WIRING DIAGRAM

Idle Speed Control Circuit:

INSPECTION PROCEDURE