2019 Sierra 1500 5.3/8-speed - trans died at 67MPH

Mike Travis · April 28, 2020

New Poster; greatly enjoyed reading the posts. My issue:

2019, 10K miles, 5.3, 8-speed, 4WD. Driving down the freeway at 67 mph with cruise and suddenly, the truck jerked hard, braked hard, lit up the dash with too many messages to read, but did not drop out of cruise control. I was then running at 4K RPM to maintain 60 mph. Got off the freeway, and discovered that I had no reverse, and what appeared to be 4th gear only (rev to 3000 RPM to get rolling). Called OnStar - they could communicate with the truck but got failure codes attempting to talk all the onboard systems - TCM, BCM, Airbag, engine - 30 minutes - and could not talk to the truck. Made it home (saturday night) let it sit till Monday morning and it started and shifted just fine on the way to the dealership. The dealer said it was the engine speed sensor and they replaced it and to come get my truck. When I did, the porter driving my truck ip only got to the edge of the service drive and stopped, engine revving. Complete trans failure - no forward or reverse gears. 3 weeks later, they say updated the TCM software per #19-NA-244: Harsh 3-2 Downshift During Closed Throttle Coast Down When
Coming to a Stop- (Nov 1, 2019). There is a special note on this bulletin: Note: This calibration update will NOT address any other transmission shift or
performance concerns.

So, they can't reproduce the issue and have no idea how to fix it. Anyone seen similar issues, or this issue? Thanks!!

Colossus · April 30, 2020

Welcome. So right now it is still at the dealer while GM tries to figure out how to fix it, correct?

Mike Travis · April 30, 2020

Yes, it is still at the dealer. They are trying to replicate the issue again so they can capture some data.

Colossus · May 1, 2020

So they are trying to duplicate the issue again, does that mean that it started working fine again shortly after?

Mike Travis · May 1, 2020

Yes, they still have it ( a month now ), and the update today was that it set a U0155 code this morning - Steering Column Lock, so they reprogrammed the steering column lock module per #20-NA-021. So basically, they continue to try and replicate the issue again.

Mike Travis · May 14, 2020

Update:

The dealer found a pin pushed in on the main wiring harness connector that connects all the modules together (TCM, ECM, ABM, SLCM, ACM, etc.); while they were not able to reproduce they problem, they did drive it for 300+ miles without issue. Also with the PCM reprogramming, it really shifts well now - the hard 3-2 downshift is gone, the occasion really hard 1 -2 upshift is gone, and it really is shifting well now. Although I have only had it back for 2 days.

Also, I can't complain about my dealer: they provided me a new 2020 loaded Sierra for the duration, detailed my truck and filled it full of gas too! They had it for almost 6 weeks and did as good as I could expect for such a difficult issue.

I will post again in a month or so as a follow up to let all know if it is still ok.