Besides measuring the wires from the IAC to the PCM for continuity, you also measured them to ground? Because the problem is intermittent, i suspect a bad connection somewhere or a shaved wire which touches some metal part.
I have the same problem. Checked for air hose leakage, replaced IAC, and the PCM. The idle was at 2000 RPM constant. P0505 code after check engine light came on. 2001 4.7 V8. Idle went down after PCM was installed but started to rise a day later. Check engine came on and the code was back.
Yeh, best to have the wires checked for continuity and short to ground. I had attached the wiring diagram for the IAC at the beginning of this thread. You could print it out and take it with you to the mechanic, so that he know where/what to measure.
JEEP Grand Cherokee 4.7 Lmtd 2004
HID 8000K in low and fog / Quad Squad member
KYB Gas-a-Just shocks / Pirelli Scorpion ATR 245/65/17 - Transgo reprogramming shiftkit.
Just a short note Frank, it did take 150 miles before the new CPU finally regained it's memory. I knew it takes awhile but didn't think it would that many miles. As I said all is well now and passing emissions was a good feeling.