Troubleshooting

DTC P0505 Idle Control System Malfunction





CIRCUIT DESCRIPTION
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 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.
Intake air bypassing the throttle valve is also distributed to the injectors of each cylinder through the passage to promote atomization of the fuel.





DETECTING CONDITION





WIRING DIAGRAM





Reference INSPECTION USING OSCILLOSCOPE
- With 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