1. Valve Lifter Failure 2. While entering the [XXX] freeway and trying to merge into traffic the engine lost power and I had to swerve and brake to avoid an adjacent vehicle, and freeway traffic had to avoid my slowing down to pull over. 3.Yes, Van GMC in Scottsdale, confirmed lifter failure. 4. Yes, GMC Dealership 5. Absolutely no warning given INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

- Phoenix, AZ, USA

Camera always stays on even when i am driving camera still on my dashboard

- Deming, NM, USA

Diesel exhaust fluid heater short circuits due to poor design. This issue occurs multiple times, including after being repaired. The failure limits the trucks capabilities until it is entirely unusable.

- Plum, PA, USA

Vehicle engine went out on truck.

- Cache, OK, USA

A very strong "ammonia" odor comes into the cabin. This happens when the def fluid is going into the exhaust system for the regen process. The odor makes people inside nauseous and dizzy. Must open widows or stop and get out of the vehicle. Our GMC dealer can find no codes or problems with the exhaust system. We have also noticed that the def fluid has gone down very quickly sometimes during this event. It is random. Some days nothing, other trips 3 and four times that the odor occurs. Looking online- there have been many post about this problem.

- Frederick, MD, USA

I have a lifters problem that the dealership takes more that three weeks to fixed without a loaner car, then i have electrical problems where the truck doesn't start at all without any warning and that's it's dangerous, never now where its going happen

- Fort Worth , TX, USA

The contact owns a 2020 GMC Sierra 1500. The contact stated that shortly after refueling while driving under 15 MPH, the check engine and service emissions warning light illuminated. The contact stated that an unknown reset was performed related to TSB: 10173675 (Engine). The vehicle was not yet fully repaired. The manufacturer was made aware of the failure. The approximate failure mileage was 46,000.

- Castle Rock, CO, USA

Two times while on the freeway the service parking brake and engine lights came on and starting braking. Could not drive over 20 mile an hour. Both times taking to dealer the lights where not on and they could not find anything wrong. I even have video of it happening.

- Pasadena, TX, USA

Repeated issues with exhaust and emissions components.

- St James City, FL, USA

Found improperly installed rear seals. The truck leaked oil and had to be towed to gmc dealership in Monahans Texas to be repaired. 1 month later the truck leaked oil again.

- Kermit , TX, USA

Rear main oil seal failure causing truck to lose all oil, leaking all over truck, trail leading to drive and garage; possibility of engine seizing up while driving causing an accident, confirmed by dealer, covered by warrenty, is a known issue, no warning lights, messages, or other symptoms of problem, NHSTA has issued a bulletin for this problem

- Lockbourne, OH, USA

On Saturday, May 22, 2021, My wife was returning from fairgrounds in Waxahachie, TX. She remote-started the car, and the vehicle started. As it started to rain and was getting muddy, and the grounds are in a grass field (No large rocks, hills or debris to climb as it's cleared land), she shifted the vehicle into 4wd high incase the field was slick. She started to drive and received several warning lights, "Service ESC, Service traction control, brake light warning and check engine light". The vehicle also had a noticeable wobble to the wheel and felt off balance, jerky, and had speed limited. My wife turned the vehicle off and back on and some of the lights went off, and the vehicle did not lurch or wobble anymore. The vehicle had a tire changed at the dealer the day prior, so I am unsure if that tire change is related or not. Now the vehicle shows an alert "check engine, service emissions system". I am having the vehicle towed to the dealership tomorrow for diagnostics. All lights except the check engine light have since turned off since powering off the vehicle.

- Fort Worth, TX, USA

At about 3500 miles lifters on two cylinders colasped. Took to dealer that dealer had three weeks but fixed it. 1500 miles later at 5036 miles it happened again on a different cylinder. Number 8. the first time it was 3 and 5. the first time the dealer replaced all 8 cylinders. So cylinder number 8 was new as well. GMC has said there is nothing else that can be done to fix the issue. The second dealer service manager states that he would not trust it either to go any long distance. Also stated that they have put 3 sets in to one vehicle before. As an ase master certified technician I find this disturbing. I also was a GMC, Pontiac, Oldsmobile master technician. This is unexceptable for GM to think this is ok to take people's hard earn money and not fix there issues or make it right. I owned a 2014,2016,2018 Silverado's that had no issues what so ever. To make things worst GMC road side assistance forgot about the truck broke down in 7 degree weather with 35 mile an hour winds. For over 24 hours and several calls back to finally get a supervisor to speak to. Two dealers say that it is unacceptable except the current dealer that is dealing directly with GMC. Anyone can do a search on GM truck lifters collapsing and you immediately overwhelmed with info. It is also disturbing that a dealership service manager says we could put a new engine in and the same thing could happen. That to me is poor quality control and poor customer service. I have always been a GM enthusiasts but this will be my last one. Horrible customer service and do not build a good product or stand behind it. GM should be ashamed of there fall from grace. This all happened just driving once to work and once hauling a atv on a trailer.

- Sebago, ME, USA

Within 3 months (<4000 miles) from purchase vehicle began sputtering with hesitation, and ticking noise from engine while in motion followed by multiple alerts posting on driver display. Vehicle displays loss of power, and struggles to keep up with traffic. Check engine light flashing followed by constantly staying on, service ESC system activated, service parking brake, and steering assist reduced drive with caution lights all activated during this episode. Dealer worked on vehicle engine ( and completed on or around 1/08/2021), and replaced lifters, and oil control valve. On 01/13/2021 noticed that vehicles lane keep assist is now working sporadically, will not activate consistently when vehicle veers off the properly marked lanes on high-way/roads, and inconsistently alerts driver while in motion. The lane keep assist is suppose to correct steering, but this does not happen consistently. The collision alert system does not activate or work correctly. Noticed while driving that vehicles in front are not detected correctly, and informs the driver they are within safe distance (green this suddenly changes to yellow). In addition when vehicles in front apply brake, the collision alert system does not alert as it is supposed to, it stays in green even at extremely close range. Safety mechanisms don't appear to work correctly, and detects items that are not present. Noticed that vehicle detects lanes even on unmarked roads, and the front pedestrian alert system activates sporadically even if no pedestrians are in front of vehicle while driving. Concerned about safety features leading to hazardous driving conditions.

- Los Fresnos, TX, USA

The engine failed at 5100 miles and is currently being repaired by the dealership. I requested a new car replacement.

- Mauldin, SC, USA

There is no way to permanently disable the auto start stop on the vehicle. Several others have complained about this, no response from GM. There needs to be a firmware upgrade to the ECM to allow the owner make the decision on if that is enabled or disabled. On mine, I have to push a button each time I start the engine to disable that. Some GM vehicles don't have that option.

- Omaha, NE, USA

The contact owns a 2020 GMC Sierra 1500. The contact stated that the vehicle push start button and key fob failed to start the vehicle on first attempt. The contact stated that the vehicle started after severals attempted. The contact stated the failure occurred intermittently. The check engine warning light illuminated. The contact stated that on his way to mckenzie Buick-GMC dealer, 6500 caroline St, milton, fl 32570, the check engine warning light was not illuminated, the vehicle was diagnosed and the contact was informed that a failure code was not found. The vehicle was not repaired. However, the contact called back the same dealer and informed them that the failure recurred. The vehicle was not yet taken back to the dealer. The manufacturer was not made aware of the failure. The failure mileage was approximately 86.

- Pensacola, FL, USA

Vehicle equipped with L87 6.2L. At 197 miles engine suddenly ceased operating and would not restart. This occurred while stopped on private road. Vehicle had to be towed to dealership where they found P0300 and diagnosed broken #4 cylinder exhaust valve spring.

- Yorktown, VA, USA

My 2020 GMC Sierra brakes failed on May 22nd and ECM and now the engine and transmission are experiencing issues based on the onstar report.

- San Antonio, TX, USA

Parked truck for one hour, engine off. Came back and upon startup, received multiple errors that power steering and ESC required dealer attention. Brake pedal would depress to floor. GMC Sierra 1500 elevation trim

- Bartlesville, OK, USA