2020 Denali Diesel won't start

[BIll Gladson]

I work at a dealership and I have a customer who just bought a truck and it has not started on him three times. Won't recognize the key for about 20 minutes. When it does start it throws a code for loss of communication with the ECM. The next start or overnight it clears itself. Any suggestions? He's ready to trade back off for a Ford! 

[CRApex]

28 minutes ago, BIll Gladson said:

I work at a dealership and I have a customer who just bought a truck and it has not started on him three times. Won't recognize the key for about 20 minutes. When it does start it throws a code for loss of communication with the ECM. The next start or overnight it clears itself. Any suggestions? He's ready to trade back off for a Ford! 

I'd have him bring it in so your service department can figure it out and take care of him.  Honestly If my sales rep was browsing internet forums for an answer rather than having him in a rental with an assurance you'll take care of him,  I might switch brands too.  Maybe there's more to the story so I apologize if that's the case..

[BIll Gladson]

we have, he's set up again because I don't have a truck available for him to use. they were scratching their heads the first time. Checked all connectors, ran the history codes. Just trying to see if anyone else is having a similar problem so I can help give them a direction on where to look.

[BlancoSilverado]

New  ECU and wire harness. 

New Fob Module (i do not know what it is called).

[2018GMC]

duramaxforum or diesel place will get you more responses. 

[Tumbleweed]

I had to same issue with a 2020 Silverado High country Duramax. Stopped for fuel 350 miles from home, the truck had a half tank.  Would not start, no response at all when hitting start button, nothing but error codes on DIC. First one was 'ESC disconnected', then every time I tried hitting the start button, I would get that code again followed by various other codes. While waiting for tow, after a little over an hour, I hit the start button again.  The vehicle started and I didn't shut it off until I got home.  Took it the the dealer the next day.  No codes, and they could not find the issue.  Pretty disappointing, this is my third Duramax, and not a single issue on the the others.