2020 2500HD L5P no communications with modules

rdomeck · August 24, 2024

Hey guys. I have no communication with multiple modules on my truck. I have been searching and searching, nut can't find related threads.

I have been fighting an issue for about three days. The truck has been rebuilt. I put a frame under it and a lot of other repairs. I had it running and driving, but something was running my batteries down completely overnight. I could not get my batteries to hold a charge any more and this is when the issue started while I was starting to troubleshoot. I am getting a U0100 code.

I have communication with my BCM. I do not have it with the ECM, TCM, TBCM (Trailer Brake Control Module).

I need help!

carkhz316 · August 25, 2024

Check the ground in the engine bay that is attached to the fender support just forward of the coolant bottle on the left side. Its G114. This is the ground for the ECM, TCM, and some others. If this is the culprit, I'd assume you'd have loss of comms with more modules relating to the diesel-specific items including the reductant module and various exhaust sensors.

Barring that, list all the modules that have no communication, or the modules that are REPORTING loss of communications and with what modules that THEY can't communicate with.

The battery drain can be addressed later, as its likely a symptom of the above issues.

Edited August 25, 2024 by carkhz316

rdomeck · August 25, 2024

I have viewed and inspected all the ground locations listed with AllData. I had even sanded each location and put a good amount of dielectric grease on each during reassembly.

I would agree that it sound like a ground issue. But all of them are checking out good!

I have the following things not working.

-Fuel gauge

-Outside temp is reading -40

-Brake pad sensor malfunction

-Service Parking brake, but that is working

-Traction control light on

-TPMS light on

The following codes descriptions.

Invalid data received from body control module

Lost comm with TCM

Lost comm with ECM