Hey all, I'm trying to solve a idle air control circuit problem (P0505). Last night I tested the IACM for short to ground with a test light and found one of the wires was hot with the key off.

I guess this could be a ground wire (the IACM has two) but only one of the four wires was hot. I went to the PCM, and the corresponding pinout (#9) was hot there too, but the remaining three IACM pinouts were not.

I guess my first question here should be whether or not any or both of those pinouts should be hot with the key off.

 

So far as I know, none of them should have power with the key off..... Key on, you should see 12 volts on two wires, other two should go to ground.

 

Not so much in IAC. PCM controls all 4 wires. It is a 2-phase stepper motor. As such, there is no "positive" or "negative". It's more of an AC waveform to move the pintle in and out, not DC. Best way to explain a stepper motor: 2-thirds oof a 3-phase AC motor with Wye windings.

With that said, i would expect it to be dead with key off.

 

Yeah, it didn't make sense that it would be live. Seems like a new PCM is in order. There's one a couple of hours away. Do you think it would work to stop at the junk yard, bring a battery, and test the pinouts of a PCM to make sure it's a good replacement?

 

I'd prefer to avoid gambling on a used PCM so I tested it again. The PCM is sending around 8 volts to both wires with the key off. I removed both live IAC motor wires from the PCM and ruled out a shorted wire somewhere along the wiring harness. Does this sound like something that can be fixed by taking it to a shop to recalibrate the computer settings or do I just have a broken PCM?

 

PCM's a sealed module, not repairable.

There is an IAC relearn procedure in the DRB3 but I don't know that any non-chrysler tools would have it.