'98 Grand Prix code P0507

P0507 Idle Control System RPM Higher Than Expected.
I have a scan gauge that says the IAC is moving when I step on the accelerator, the harder I step, the higher the number, but at 2200 RPM's it reads 0 (foot off accelerator).
I have checked for vacuum leaks.
I checked the scan gauge for TPS and foot off, it reads 0%
Does anyone have any ideas? I have pondered this til my head hurts.
Thanks for any ideas.

Does the car physically idle higher then it's supposed to?

yes, it is running at 2200 rpm's when cold, then as I try to "tap" it to make it go down, it actually goes up.

2200 rpm in park at idle? It sounds like the IAC or the circuit to it is no good! Have you tried cleaning the IAC and throttle body? Any splits in the air snorkel? vaccum leaks etc!

yes, 2200 in park at idle
I inspected the IAC, it was clean as was the seat for it in the TB.
I checked the entire top half of the engine with carb cleaner, no changes in idle speed, so I guess there were no noticable vacuum leaks.

when it's running if you disconnect the iac does anything happen?

no it doesn't

Okay so either the pcm is trying to control the IAC and it's not receiving the commands, the commands aren't being sent from the pcm, the command is there but the IAC is no good or something else is causing the idle to be too high and the IAC at maximum extension still isn't enough to pull the idle down to where it should be! Some better quality noid light kits have IAC lights in them that flicker as the IAC is pulsed, if you could bet you hands on those it would help in determining whether the command is there or not, If not you''ll need a dvom and a wiring diagram to start checking the circuits!

I thought about tracing the wires from the IAC to the PCM, damn rain stopped me from doing that today.