LBZ IAT & IAT2 PIDs

[Cougar281]

Ross, we had discussed the LBZ IAT & IAT2 PIDs in this (http://forum.efilive.com/showthread.php?16844-Pre-Release-Update-July-18-2011/page2&highlight=IAT2) thread and you indicated you were going to look into what was going on. Have you made any progress?

[GMPX]

No, please remind me what the problem is.

[Cougar281]

There is no IAT2 (IAT2 is the second sensor, which is in the intake bridge), and PID listed as IAT is actually the IAT2 sensor. You had suggested looking at SAE.AAT, but I have no idea where that's coming from as when I unplug the MAF, it remains unchanged.

I get both IAT and IAT2, which when disconnected, go to -40 (open circuit) on my Tech2.

The IAT and IAT2 PIDs are correct on the LMM ECM.

[JoshH]

Have you looked at this thread: http://forum.efilive.com/showthread.php?11323-IAT2-or

[Cougar281]

Have you looked at this thread: http://forum.efilive.com/showthread.php?11323-IAT2-or

Yes, and I posted in it several times and have posted the following (somewhat paraphrased) several times:

EFILive's SAE.IAT reads what is actually IAT2 (The sensor in the Y-bridge). AAT is pulled out of thin air. I tried unplugging each sensor and AAT never fluctuated. Unplug the IAT2 sensor and IAT goes to -40.

On a LMM Efilive's SAE.IAT reads the IAT sensor (the one in the MAF). SAE.IAT2 reads the sensor in the Y-Bridge. not sure where Killerbee gets "AAT is measured post CAC/Pre EGR", but to the best of my knowledge, the LBZ & LMM have all of the same intake temp sensors.

On the Tech2 I get proper reading for IAT & IAT2, and get -40 on each when their respective sensors are unplugged on both a LMM & my LBZ.

I know IAT & IAT2 are valid & defined PIDs because I've seen them both in the available PID Lists for Ease Diagnostics scan tool as well as AutoEnginuity's tool.

[JoshH]

The AAT changes on my truck when I unplug the MAF sensor. Yours doesn't?

[GMPX]

From the GM wiring schematics I have (genuine service manual), it's printed like so:

LBZ:
IAT (with MAF) on wiring diagram = IAT Sensor signal on pin-out, pin X1,42
IAT2 on wiring diagram = IAT2 on pin-out, pin X1,65

LMM:
IAT (with MAF) on wiring diagram = IAT Sensor signal on pin-out, pin X1,42
IAT2 on wiring diagram = Air Temp Signal on pin-out, pin X1,65

So you can see it's the same sensors going to the same pins.

The PID "GM.IAT2" is reported as supported by the LMM only, lets assume this is the 'Air Temp Signal'.
The PID "SAE.AAT is reported as supported by the LMM & LBZ, lets assume this is also the 'Air Temp Signal', because.....
The PID "SAE.IAT" is reported as supported by the LMM & LBZ, lets assume this is the 'Intake Temp Signal (with the MAF)'.

So if the LMM supports SAE.IAT, SAE.AAT & GM.IAT2, what the heck is what?

[killerbee]

I recall that AAT had big swings over short time intervals (undampened response), suggesting it is the MAF area, or possibly in the grill.