U18A2

[Andy2016]

Ive been chasing this coms fault for awhile, it's ecm is not communicating with the FPCM, at first I read 120 ohm on 6 and 14, I replaced the FPCM, it was programmed already from GM, replaced end of 2025. Over the past week Ive had time to start by cleaning grounds, removed the wire loom at the rear of the truck to expose all of the wires to the 4 modules above the spare tire, Ive removed all connecters and inspected, after I checked ohms from the resistors through every module with connecters back in. Its weird, must of had a pin that had pushed up, now Im getting 60 ohms, voltage is good also, still not communicating. I have 2 more ground that are on top of the dash to do and see if that fixes it. Ive checked the BCM, FPCM, TRCM, SPCM, ECM, main fuse box connecter, both side dash fuse boxes etc. Any other ideas would be great. Truck is well taking.

[Andy2016]

CanHI 2.8 CanLo 2.2, nothing to Chassis ground from Pin 6 or Pin 14, 60 ohm on Pin 6 and 14, checked every connection, cut and removed tape from the middle of the truck to the rear, opened up dash also. Im leaning towards a bad FPCM again. Couldn't be bad straight from GM could it, hopefully warranty is still good, got the new one back in June of 25 and the light and code never went away after clearing codes. I furgured the new FPCM could not be bad and some have said a wiring issue, thats why Im at this point.