2020 GMC SIERRA 1500 Complaints

Transmission failed at 75,000 miles, yes it is available for inspection. Truck went into limp mode on the highway and turned into a very dangerous situation, I was barely able to exit the highway. Yes the dealership Martys GMC in Kingston MA has confirmed that it is transmission failure. My vehicle has been sitting on the lot of Marty's GMC since September 13, 2024 waiting for a backordered part to fix the transmission at an estimated cost of $2,500. The warning check engine light followed by every single lamp on the dash appearing on [XXX] which is the date of transmission failure. After careful research of this issue I have found this is a widespread problem with this particular 10 speed GMC transmission in my 2020 GMC Sierra that I am still paying car payments on. I have rented a vehicle at my own cost for the past 4 plus weeks to get back and forth to work. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

The contact owns a 2020 GMC Sierra 1500. The contact stated that while the vehicle was parked and being driven, the vehicle was shaking violently. There were no warning lights illuminated. The contact stated that the failure was related to Technical Service Bulletin: 22-NA-186. The vehicle was taken to a local dealer, where it was diagnosed that the motor mount brackets needed to be replaced. The vehicle was repaired, but the failure persisted. The manufacturer was contacted, opened a case, and referred the contact to the NHTSA Hotline for assistance. The failure mileage was approximately 100,000.

On two separate occasions, while traveling at highway speeds with the adaptive cruise control system on, my truck randomly started braking hard as if it was sensing a vehicle or obstacle in front of me but my lane was completely clear. The most recent time, I was almost rear ended because of this issue.

The contact owns a 2020 GMC Sierra 1500. The contact stated that the vehicle failed to start. The battery was replaced, and the failure was remedied. On another occasion, the contact stated that the brake percentage was low on the instrument panel and that the lights were becoming dim. The vehicle was taken to a dealer where the brakes were replaced; however, the computer failed to detect the repair; and the message "1 More Mile Left to Drive" was displayed. The contact also stated that two weeks later while driving 45 MPH, the brake pedal failed to respond and felt abnormally loose. The vehicle was driven over a concrete sidewalk to stop the vehicle. There was no crash, and no injuries were sustained. The vehicle was towed to the residence. The vehicle was not diagnosed or repaired. The manufacturer was notified of the failure and confirmed that the VIN was not under recall. The approximate failure mileage was 102,000.

My truck 2020 gmc sierra 1500 AT4 denali is not working properly since July 2024. I took it to 2 different dealership to get a diagnostic and i finally ended doing the repairs for brake issues. I have been towed 6 or more times and almost experienced 2 car accidents since I drive the truck after the supposedly repairs where done but i ended stranded again with no brakes. The dealership has repair the truck 3 times but im still getting sevaral codes the fact that i had to pay out of pocket and have to deal with this and expose myself to danger and my family in driving a vehicle that is no safety condition its absurd. I call several times the recall GM hotline and i was told GMC 1500 are included in the recalls just not the AT4 and i have a family member with the same truck and same issues she ended up trading in the truck recently since she kept experiencing the same issues over and over again just like me.

My brakes failed 2 times. One time I almost got into a horrible wreck with my daughter in the truck. "Brake system failure" " max speed 43mph" I have not had any brake work or anything done. The dealer is trying to charge me to replace the whole brake system when [XXX] this says to reprogram. Still waiting on gmc to tell me if it's covered under warranty. From my own research this has been a major problem for hundreds of people if not more. I could have died because of a faulty brake system or a bad software update. I need help with this and so do the countless other 2020 gm owners. There is a recall on the 2019 for the exact problem but not the 2020s. GM safety recall N192268090 please advise INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Without warning power steering went out. Flashed code: service power steering; service esm and traction control light. After two restarts, went away like it never happened. I was backing a 24 ft trailer at the time of occurrence. There are numerous other people with the same problem in online forums. I cannot believe that there has not been a recall or even service bulletin regarding this problem. It is a MAJOR safety concern

The AFM/DFM system in these trucks are making the engines and transmissions go out around 70k miles. The lifters fail right around the same time factory warranty runs out then your left with a 6 thousand dollar bill to have it fixed. I hope this becomes a recall because numerous people I talk to are getting rid of they're gmcs and chevys and going elsewhere.

The transmission went at 67,000 miles and posed a safety issue when my husband was driving & suddenly couldn't drive above 1st gear. Vehicle is at the GM dealer and has been for weeks, but there have been so many issues with the transmissions of this year, make & model, that the transmissions are on back order and we are told it can be MONTHS before they get one in. The dealer already has another one that has been waiting for once since April. We know of others with this same issue on this make/model/yr, as well as engine issues, but yet there are NO recalls for this issue. The only warning that came on was when the issue occurred- no prior warning or indications. GM is involved but make no comment on why there isn't a recall for an obvious known issue.

The contact owns a 2020 GMC Sierra 1500. The contact stated while driving at various speeds, the vehicle was stuck in gear. While driving there was an abnormal burning odor coming from the vehicle. The vehicle failed to start on several occasions. There were sparks from the passenger's side front seat. Several unknown warning lights were illuminated. The vehicle was taken to the local dealer, where it was diagnosed with electrical, transmission module, wiring harness, air alternator cooler, and exhaust system failures. The vehicle was repaired; however, the failure recurred. Additionally, while driving at undisclosed speeds, there was a failure with the vault meter. The OnStar system provided an error with the antilock braking system. The manufacturer was contacted, but no assistance was provided. The failure mileage was approximately 44,000.