Hey guys, hoping someone here has dealt with something like this because I’m going in circles.
So I bought a 2014 C7 at auction knowing it was going to be a project. Came with the ECM connectors literally torn off and no ECM, so ultimately it doesn’t start or crank. No big deal I’ve done stuff like this before, figured I’d source what I needed and get it sorted.

So I bought a replacement ECM off eBay from a guy I’ve actually used before with good results, programmed to my VIN. Also grabbed the exact and complete engine harness off a 2014 parts car so I’d have clean connectors and everything matching. Got it all swapped in without pulling the engine which was a whole adventure by itself..

Fired up the scanner and immediately got U0100 all over the place. Lost comm to ECM from basically every module on the car. Car still won’t start, and won’t crank.
Brought in a local guy who programs keys and ECMs and he couldn’t talk to it either with his tool. So it’s not a me problem, the ECM just isn’t communicating at all.

At this point I’m thinking it’s either a power or ground issue, something with the connectors since the originals were ripped off, a CAN bus problem somewhere in the harness, or the ECM itself is just bad..

Has anyone dealt with a C7 that had the ECM connectors torn out or has had to replace the ECM? Any known weak spots for grounds or power feeds on these I should be checking? Any main wires I should be checking that could prevent it from starting?

I’ll take any advice I can get at this point, thanks!

 

Blown fuse?

 

checked the fuses and also have a fuse box from the parts car too that I was switching fuses back and forth with, and still nothing.

 

For any module "No Comm" you always check that modules powers and grounds.

 

yes I did. it was driving me crazy not finding anything.. it turns out it was a 10amp fuse in the back that was blown!

 

Yea if you ever see everyone throwing codes against one module and you can't talk to that module with a scan tool its either totally dead or its a power/ground/wake-up (some modules have an ignition line to wake) issue. Luckily in this case it was merely a fuse and not a bad wire.

 

Check your CAN network. You have a communication problem. There are a few videos on You tube that go into diagnosing the Can network. It would take me all night to explain.