OBD II code for Idle Control System malfunction

ROBERT CATES

MEMBER
1996 SUBARU LEGACY
2.2L
4 CYL
AWD
AUTOMATIC
240,000 MILES

Car was fine one day then the next would not run. Will start but soon stalls out. CEL came on with a P0505. Have checked all vacuum lines and can not find a leak. I have noticed that the IAC valve continues to be energized for a while after the engine is turned off. I was told by a parts dealer this means that the motor has an internal short and needs to be replaced. As I know he would love to sell me a $350 part I thought I would get a second opinion. I have pulled and cleaned the IAC. Is there a simple test to determine if the motor is bad? There are three prongs on the wiring connector. Could a fault in the ECU cause the IAC to continue to receive power? I would think this could also be a symptom of weak fuel pressure, but would that throw a code?
Thanks.

3 Replies

WRENCHTECH

MECHANIC
20,761 POSTS

I don't know how you concluded that the IAC is active after the key is turned off but it should not be receiving any power supply with the key off. The main relay supplies that.

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Tuesday, April 22nd, 2014 AT 3:10 AM

ROBERT CATES

MEMBER
2 POSTS

I can hear it buzzing. When I pull the wiring harness off it stops. This is true even with the IAC removed from the manifold. Turning the key to on, then back off, you can see that the valve is torqued, and hear it buzzing, until you remove the harness.