GMC Complaints

Subject: Event of engine failure • While driving on a level paved road at 15 miles per hour in a busy area my 2019 GMC Sierra Denali pickup truck stalled in the middle of a busy street. • Truck stalled in a heavy traffic area at an intersection putting myself and passengers in a dangerous area and situation. This obstructed the normal flow of traffic causing a danger to pedestrians and normal vehicle traffic pattern. Each had to go around my disabled truck into oncoming traffic putting them and normal traffic flow at risk. •Upon securing a towing service the truck was transported to the nearest GM dealership. This happened on a Friday afternoon and the truck got to the dealership after hours. I returned to the dealership the next morning and was told that they may not be able to check the truck until probably Tuesday. On Monday afternoon I called and they hadn't been able to get to it. I received a call the next day and was informed that the technician at the dealership had put a breaker bar to the crankcase and the engine would not move and therefore the engine is seized. • There were no warning lights that came on prior to the truck stalling in the street. There was no noise prior or any other symptom to give any indication that the truck was not operating in a normal fashion.

No Incident Occurred. Tire Size 275/65R20. Tire Pressure Fluctuating between 59 and 71 PSI. 3 of 4 tires appear to have a defect. Was detailing the vehicle on 7/26/26 and noticed a tear in the Side wall on the Passenger side rear tire. About 3/4" to 1 inch away from the rim along the sidewall. Running parallel with the rim for about 4". Found similar defects and indentation lines on the Passenger side front and Drivers side rear, in varying lengths around the rim. Vehicle has Not Towed, had a Load in the bed or used off road. 1,897 miles all Pavement Mixed HWY and Street use. Vehicle was Purchased 6/25/26. Scheduled for Service 7/28/26. Will have the Dealer look at the tires.

My vehicle keeps showing a front camera warning and we went to the dealership multiple times and they were unable to diagnose the problem. This seems to be a widespread common problem among many owners and it’s a safety concern affecting parking and forward collision.

The engine (6.2L V8) in my 2024 GMC Sierra 1500 AT4 failed at approximately 40,750 miles. I began hearing a ticking noise coming from the engine, and the dealership subsequently diagnosed the cause as damaged bearings that in turn damaged the crankshaft, requiring a full engine replacement. Notably, this vehicle was not included in the related recall covering this engine defect, despite exhibiting the same failure. The original failed engine may be available for inspection upon request but I would need to confirm with the dealership whether it was retained or already returned to GM under warranty. This defect creates a serious safety risk because a damaged crankshaft and bearings can cause the engine to lose power or shut off without warning while driving. An unexpected loss of engine power at highway speed or in traffic could result in loss of vehicle control, reduced ability to accelerate out of a hazard, and increased risk of a collision to myself and to other drivers on the road. The failure gave no advance warning, so there was no opportunity to pull over safely before the issue became apparent. The fact that this failure occurred outside the scope of the existing recall suggests other vehicles with the same defect may be similarly at risk without notice. The dealership diagnosed damaged bearings and a damaged crankshaft as the cause of the ticking noise and performed a full engine replacement under warranty, confirming the failure. The dealership diagnosed the failure and performed the repair; I do not have direct confirmation of whether GM's engineering or warranty division conducted a separate inspection of the failed components beyond the dealer-level diagnosis. No warning lights or messages appeared on the dashboard at any point. The only symptom prior to failure was a ticking sound from the engine which I noticed shortly before the engine required replacement. I was not provided any electronic warning that would have alerted me.

While driving enroute to a concert in [XXX]., in the passing lane on [XXX] around [XXX] & just before exit 22(mile marker 21) during rush hour on 7-23 at 5.09pm, my truck abruptly lost power and shut off! It would not start, I could not engage "N" from "P" to attempt to push my truck to the far left side of the highway. This was a "VERY DANGEROUS" situation as I could have been rear ended or much worse! I immediately called SOS/ON STAR for assistance. In the meantime, a police officer and state troopers showed up to divert the traffic around my truck. Eventually, a "HERO" vehicle showed up and at the direction of the police, my truck was "DRAGGED" from the passing lane to the emergency lane. As for getting a tow truck, 1 finally showed up after 5+ hours. I found out the you all have a contract with "AAA", which is the worse when it comes to getting any assistance. I was towed back to [XXX] to South Town GMC dealership & arrived at 11.25pm. It was only the next morning that I received an email from OnStar dated 7-23 at 5.07pm, with an "Advance Diagnostics" advising of a critical issue with the engine & transmission. The code was: P129F, which is the fuel pump and/or module. My truck now sits at the dealership with a dead battery, waiting for them to address. I have heard that there are issues and recalls in certain vehicles with this similar issue. I do have "extended warranty" protection thru Ally that I bought. However, the shock is finding out that the only way to get it into "N" is a special dealer tool that goes into the transmission under my truck! Are you SERIOUS??????? To have no ability to put my truck into "N" is not only unacceptable, but extremely dangerous. Especially with what happened to me & my family. At this point, I am at the mercy of my dealership to find the time to address this issue. Until then, I have no transportation & very upset with the stress of all that happened! INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B

Knocking sound and flashing engine light came on. When brought to dealership it was determined that lower bearing failure took place requiring full engine replacement. '

While towing my trailer the vehicle intermittently slams gears and will hesitate the back tires momentarily to the point of screeching. This has led to close calls being nearly rear ended and having to pull over. This started out as a hard slam while trailering on the highway and has progressively gotten worse. Had into dealership twice to multiple times to try and figure out the issue but it’s not throwing any codes and they can’t get it to duplicate the issues. Nothing can be replaced due to no codes even though they think the valve body is going bad. Leaving the vehicle as a ticking time bomb for failure which could result potentially in a catastrophic incident. Only had the vehicle for one year now has 37k miles on it and have had the ecm, full wiring harness, and multiple sensors replaced already for a different problem early this year that had the truck in the shop for a month.

6 month old, 9,000 miles 2026 Sierra 1500 with Duramax 3 liter suffered an engine control module failure 4 hours into a 12.5 hour drive home from family vacation. First a transmission service warning flashed, then an emissions system failure with a forced speed reduction warning. This happened with two children and a dog in the vehicle. OnStar did diagnotics and said I had to see a dealer. Fortunately one was nearby and they determined the engine control module needed to be replaced--but i was 8.5 hours' drive from home with kids and dog and would have had to stay for 2-4 days awaiting parts and repair. I traded the truck at the dealer for a new vehicle and drove that home. This was a major safety concern traveling with children and a dog on a nearly 100 degree day. And it was a brand new vehicle.

Vehicle: 2021 GMC Sierra SLT | VIN: [XXX] Dealership: Carl Black GMC Roswell, GA (11225 Alpharetta Hwy, 30076) | Invoice #[XXX] | Service Date: [XXX] Paragraph 1 – Suspension Hazard: Dealership diagnosed a worn left upper ball joint (popping sound on left turns) and installed Rough Country aftermarket upper control arms on my stock-height Sierra SLT. These arms are designed for lifted suspension and alter factory caster/camber geometry, placing extreme stress on ball joints. This can cause sudden ball joint separation, wheel collapse, and total loss of steering control at speed. The dealership admitted on the invoice they "could not find branding" on original parts and chose non-OEM lift components without my consent or any safety disclosure. Paragraph 2 – Brake Failure & No Safety Warning: The same service included a full front/rear brake job (pads + resurfaced rotors) using their certified technicians and parts. After pickup, the brakes failed to operate properly. When I returned, the service manager refused to correct their own workmanship and instead quoted $1,900 to repair the very brakes they just serviced. Most critically, at vehicle pickup they issued no written or verbal safety warning—no "do not drive" instruction—despite the brakes being knowingly compromised, endangering me and the public. Paragraph 3 – Requested Action: The service manager was unprofessional, condescending, and refused accountability. I request an immediate NHTSA investigation into Carl Black GMC's unauthorized use of lift-kit suspension parts on stock vehicles, failure to warranty their own brake service, and reckless omission of safety warnings at delivery. This dealership pattern poses an imminent public risk. Please escalate. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

The contact called on behalf of an insurer who owns a 2026 GMC Sierra 2500. The contact stated that 15 minutes after the vehicle was parked and turned off, a neighbor informed the owner that the vehicle had caught on fire. The owner and the neighbor extinguished the fire using water hoses. The contact stated that the fire originated under the rear passenger’s side seat and was caused by an overheating amplifier that had short-circuited. No warning light was illuminated. The Fire Department responded to the scene and filed a report. There was no Police report filed. There was no injury or property damage. The vehicle remained parked, and the owner intended to return the vehicle to the dealer. The owner was provided a loaner vehicle. The vehicle was not diagnosed or repaired. The manufacturer was notified of the failure, and a case was opened, but no assistance was provided. The failure mileage was approximately 9,000.