2008 Denali XL possible ECM Failure?

[Doubeleive]

I figured out that it is just some weird thing with that pin and everything is fine. Regardless, the FPCM indicates that the engine never commands the pump to run. I got rid of the dorman module and got an AC delco one just to check. I saw some places to check the dark green/white stripe wire on the connector. The wire is fine and has good continuity through to the pin, but I am not sure where to follow that wire to? I gather from looking at the wiring schematics that it goes directly there and is just a signal wire. I can make a jumper to test this, but would need to know which wire to mess with, if someone can help?

you've dug a bit farther than I have into the diagnostics of the fpcm at this point, I am sure the ecm commands the pump so the good news is if you get a used ecm it will only cost you $40 to program it thru tis2web. as far the pin32 you have to keep in mind most of the modules on these trucks run on a high speed lan/serial bus so the signals are digital, jumping that wire may or may not do anything.

 

[Rich Reno]

So... there is something wrong with the wire that runs from the ECM to the FPCM that has some kind of internal short in it somewhere. There is no damage to the loom, the wires, or anything from point A to point B, yet the signal never makes it to the FPCM. Ran a new wire and everything fires up no problems. I plugged the old FPCM in and it was fried, same with the old ECM. So the whole thing must have started with the wire and it created issues with both modules.

http://gmflash.com/fscm-diagnosis

This is the diagram that I used to verify the pin and wires on the FPCM, and while not perfect, I used this http://lt1swap.com/E38 ECM Connector Pinouts.htm to check the ECM side of things. I wish I could point to a reason why it happened, but I am not sure without pulling the full harness and testing the wire along the full length.