Troubleshooting

DTC P0505 Idle Control System Malfunction

CIRCUIT DESCRIPTION

System Schematic:

The step motor type IAC valve is located in front of the intake air chamber. 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 four 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.





DETECTING CONDITION





WIRING DIAGRAM

Reference Waveform - IAC Valve Open:

Reference Waveform - IAC Valve Closed:

Reference INSPECTION USING OSCILLOSCOPE
- With the engine idling measure waveforms between terminals ISC1, ISC2, ISC3, ISC4 and E01 of ECM when A/C switch ON or OFF.

HINT: The correct waveforms are as shown.

Step 1:

Step 2:

Step 3:

Step 4:

INSPECTION PROCEDURE