P1504 - Idle Air Control (IAC) Circuit Malfunction

This DTC is set when the PCM detects an electrical load failure on the IAC output circuit.

IAC circuit open
VPWR to IAC solenoid open
IAC circuit short to PWR
IAC circuit short to GND
Damaged IAC valve
Damaged PCM


The IAC solenoid resistance is from 6 to 13 ohms.

 

Thanks for the response. I will check it tomorrow morning when I get my hands on a multi-meter again. How do you check the PCM or is that too sophisticated for my multi-meter?

 

I would check the OHMs of the IAC. Disconnect the IAC plug, set the meter on OHMs and see if the IAC pins read between 6 and 13 ohms.

 

Ohms were 11.5, all vacuum tubes were solid, and I replaced the grommet on the PCV valve entering the valve cover. It was pretty worn and looked like there was a gap that air entering. Could this cause the fault code for the IAC Valve? I haven't had the problem since but still noticed some rough idle when the car was sitting today with the AC compressor engaged.

Any other advice?

 

Have you disconnected the battery and let the car relearn idle?

 

I did that, and the car is still having the same problem. However, if I have the vent setting to off or dash, (A/C compressor off) the car starts and idles a little better without dying. The car definitely dies when the pump is engaged. Take it to the dealer or any other suggestions?