2021 GMC SIERRA 1500 Complaints

This truck, along with many others, has had wiring harness issues. My truck has fought this issue within the first six months of owning the truck. Since Jan 2025 it has left me stranded 3 times to be towed, and in the shop a total of 6 times for wiring harness issues. Rubbing that GM is 100% aware of how its designed. This has caused the truck to hesitate, shake, lunge, go in and out of gear severely hard then shut off while driving. All three time this happened to me recently i was on the interstate. GM has work orders out with all the codes and symptoms but wont do anything about it. Yes, i am out of warranty, but i am now paying over $5,000 for a new harness to be installed by a different dealer. The dealer that had always worked on this truck requested $8,100 so i called a new GM shop. This is a large issue and they keep turning their back and not addressing the issue and putting drivers at risk! Can provide last diagnostics and can request all notes from Stoops Buick GMC in Muncie Indiana, i have a rather large file there on this truck.

My tailgate will randomly open on its own. I’ve had several instances( 5 or 6 times so far) when I’ve had open on its own. Only once so far when i was driving. Luckily, i was on my private road without anything in my bed that could fall out. I often carry mountain bikes over the tailgate which could pose a serious danger if the tailgate were to open when driving. Also earlier this evening when the tailgate came down on its own while driving, when I got to my destination, I was unable to open the tailgate at all from outside the vehicle. It is apparent the button to release the switch is malfunctioning. I was able to get it to open by using release button inside the vehicle.

Engine failure. Engine Locked up and truck shut down in the middle of the Freeway. Barely made it to the side of the road.

Driving on highway at approximately 70 mph and the engine completely cut off without warning. Error message on dash said put car in neutral and press the start button. After safely pulling over, the vehicle was never able to start or even crank. Towed back to the dealership. Catastrophic engine failure according to the dealership. Vehicle has the 6.2 V8 engine with known issues by GMC apparently. Only 32k miles and under warranty but dealership reports that replacement engines are on back order and they have not been able to source one.

Transmission will slam hard then truck goes into low power mode and doesn’t shift.

The contact owns a 2021 GMC Sierra 1500. The contact stated while the vehicle was parked, the contact attempted to turn off the vehicle; however, the vehicle remained running. A message was displayed to shift to park(P). The contact stated that the lights, radio, and other functions remained operational. On another occasion, the vehicle jerked, and the steering was difficult to turn. The dealer was contacted; however, the vehicle had not been taken to be diagnosed or repaired. The contact also stated that the trunk failed to fully close. The message that the trunk was open was displayed. The contact attempted to close the trunk and message on the displayed was turned off; however, the trunk remained slightly open. The vehicle was not taken to be diagnosed or repaired. The manufacturer was not made aware of the failure. The failure mileage was approximately 63,315.

At cold start-up, engine (6.2) makes a metal-to-metal grinding sound for 60-90 seconds. After warm-up, a steady tick on the right side of the engine while running. I contacted GM and they said, " this was normal at start up". however, with me being a mechanical engineer, all of my school and working experience tells me anything grinding metal to metal is not good.

The contact owns a 2021 GMC Sierra 1500. The contact stated while driving at 50 MPH, the transmission independently downshifted and the rear wheels seized. The contact stated that the rear wheels skidded. In addition, the contact noticed an abnormal clunking sound. The vehicle was not diagnosed or repaired by an independent mechanic or dealer. The dealer was made aware of the failure. The contact stated that the failure occurred immediately after the recall repair under NHTSA Campaign Number: 24V797000 (Power Train) was performed by the dealer. The manufacturer was not made aware of the failure. The failure mileage was unknown.

I own a 2021 GMC Sierra 1500 Duramax diesel. At around 60,000 miles, I received an engine coolant system alert through OnStar and retrieved a P1098 trouble code, which indicates a failure in the coolant control valve. This issue causes the engine fan to run excessively, creating loud noise, reduced fuel economy, and possible drivability concerns. After researching owner forums and talking to multiple service departments, I discovered this is a widespread problem among 2020–2022 GMC/Chevrolet Duramax 3.0L diesel owners. In many cases, the coolant control valve is failing prematurely, and the replacement part is on national backorder, suggesting a high failure rate. GM has not issued a recall or service bulletin to address the issue, and many customers are being told to pay out of pocket despite the systemic nature of the failure. This component is tied to engine temperature control, and failure could pose a safety risk if the engine overheats or derates unexpectedly. I am filing this complaint to document the issue and request NHTSA investigate this as a potential defect.

The contact owns a 2021 GMC Sierra 1500. The contact stated that while driving 30 MPH, there was an abnormal knocking sound coming from the engine compartment, after which the vehicle lost motive power. The contact was able to pull over to the side of the road. No warning lights were illuminated. The vehicle was taken to a dealer, who determined that the engine needed to be replaced. The vehicle was repaired. The contact stated that prior to the engine failure, the transmission was replaced. The manufacturer was not notified of the failure. The failure mileage was approximately 20,000.