IAC Troubles (electrical)

[diryarimort]

90Celica 2.2L

*IAC - Resistance OK (I have a spare that works as well, though both are used)

When the IAC is attached to the car (not even plugged in) I get High Idle 1900+rpm with surging of +-300rpm. Plug it in and you get slightly higher Idle with a faster surging. (all of this happens regardless of the engine temp).

Undo the two screws and remove the IAC and run the car, Everything is OK, idle at 900rpm.

With the car running at temp
Checking the IAC harness I get 13v across ISCC and B+
And I get 12.5v across ISCO and B+

ECM shows no faults.

Should I be getting voltage across both terminals at the IAC?? or is this a wiring or maybe ECM fault?


Info about the car and what I've tried so far:
MAP, Timing, Coolant temp sens, TPS all OK.
No vacuum leaks, EGR and emissions systems working.
Car runs like a champ and pulls hard.

Thanks in advance