IAT issues with E38 pcm

[V8R]

Hello,
E38 pcm that came with the donor engine from a 2015 Camaro LS3. Using the card style maf with integrated iat in a Z06 intake. Calibration and part number match 2015 Camaro. Scanner reads -40 for air intake and occasionally get a P0113 code. I have used this same set up for multiple conversions.
I have tried:
-new GM maf sensor
-known good e38
-pinned all 5 maf wires back to pcm- have continuity and all are going to proper pins
-check resistance on pin e- signal for iat. It showed correct resistance for the current ambient condition.
- confirmed calibration table- checked stock file in repository
What am I missing? Thanks for any help.

[TheMechanic]

-40 is open circuit. Are you getting 5v reference to the sensor? Getting a 5v reference all the way to the PCM if you take out the signal return pin on the ECM connector?
Knowing this you might be able to zero in a little further.

[edcmat-l1]

With your key on engine off and scanner running, wiggle the wires right at the MAF connector. I'd bet either a pin has loosened up or a wire is broke inside the insulation, something along those lines. Wiggle test should tell you.

Have someone watch your scanner as you wiggle the wires. Bet it flickers to life.

[TheMechanic]

With your key on engine off and scanner running, wiggle the wires right at the MAF connector. I'd bet either a pin has loosened up or a wire is broke inside the insulation, something along those lines. Wiggle test should tell you.

Have someone watch your scanner as you wiggle the wires. Bet it flickers to life.

Especially if it is a yellow wire.

[edcmat-l1]

Especially if it is a yellow wire.

That's the one LOL

[V8R]

-40 is open circuit. Are you getting 5v reference to the sensor? Getting a 5v reference all the way to the PCM if you take out the signal return pin on the ECM connector?
Knowing this you might be able to zero in a little further.

There is no 5v reference to the maf. A-E are: Maf signal, serial ground, 12v, ground, iat signal.

[V8R]

Just did a wiggle test as well. No love there. I'm going to run a new wire from the iat signal pin to pin 37 on the blk pcm connector and bypass the rest of the harness and see what I get.

[blindsquirrel]

IAT signal should be ~5v when unplugged, there is a pullup resistor inside the ECM. The IAT sensor's resistance determines how much of that voltage bleeds away to ground, the ECM monitors how much voltage is left over to figure out what the temperature is.

If there is no voltage on the IAT signal wire when unplugged you have a bad wire or a bad ECM (or it's pinned to the wrong location in the ECM connector).

(generic E38 diagram, I don't have 2009+ manuals... but you should if you're working on this stuff)
screenshot.14-09-2023 17.32.58.png

[V8R]

Fixed! As everything checked out, I ordered a third maf. Last one was brand new from GM. This was an aftermarket Hitachi. Reads as it should in the logger. Thanks for all the help.