While I am tracking down this intermittent IAT sensor issue (IAT signal goes high intermittently), I figure I'll post the info I've found so far in case anyone else needs to troubleshoot something like this.
First there is the pinout diagram of the 5 pin MAF/IAT connector itself:
From what I can tell, the orientation of the connector is looking directly at the front end that plugs into the connector on the MAF housing itself.
Then there is the wiring diagram schematic of the circuit:
You can see the IAT sensor indicated as a thermistor, which is a variable resistor that changes resistance based on temperature. It's the squiggly line with the arrow catecorner through it.
And here's a pic of the back of the MAF/IAT connector on my own car showing the wiring colors:
And here's a pic of the socket right on the MAF housing where you can plainly see the left two pins apparently part of the IAT sensor itself in that oval plastic insert:
And here's a pic of the connector itself:
Someone posted a description of the wires with pinouts both at the connector side and at the PCM side:
Quote:
Delphi 5-Pin MAF
Connector Pins, left to right, looking into inlet
(Left)
1 IAT output, to IAT harness, TAN (tan), to PCM C2 Pin 25
2 IAT reference, to IAT harness, PPL (purple), to PCM C1 Pin 57
3 MAF ground, to MAF harness, BLK (black) to main ground dist.
4 MAF power (IGN), to MAF harness, PNK (pink) to ENG SEN fuse
5 MAF output, to MAF harness, YEL (yellow) to PCM C2 Pin 31
(Right)
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There is a problem with this description in that it appears that the TAN and PPL wires are switched, so bear that in mind. But since they appear to just reference each other through the resistance of the IAT sensor, then I don't think polarity makes any difference.