Casper2020

I've got a 2012 chevy express 3500 that currently is crank but no start with code U0121 (TCM lost communication with brake control module). It has been having intermittent issues where it would flash 'service traction control' and the ABS light would come on while driving, but then would immediately go away and no other symptoms. Today it did the same thing but this time the van lurched forward before the issue went away and 100 feet later (at 5mph in a parking lot) the van completely turned off and would not start again. Why would an ABS code cause the van not to start? Apparently the 12V 'wake up' wire for the ABS module is split with the fuel pump which maybe explains explain the lurch and why it won't start.? Any thoughts on this?

mountainmanjoe

make sure modules have power, ground, and CAN signal. If they do, and still can't communicate then its failed.
Happened to my TCM. $700 to replace and reprogram.
Bravo GM.

Triaged

https://m.youtube.com/watch?v=qVCklDoXbHAGive that a watch. Look for some bad wiring.