2025 GMC Sierra 1500

The engine seized and locked up leading to a catastrophic failure of my three month old 2025 GMC Sierra Denali at approximately 3,181 miles. The engine, the 6.2L V8, was listed as a recall engine by GM for model years 2021-2024. My 2025 allegedly "passed inspection" yet had the same catastrophic failure. The vehicle engine made loud noises and it sounded like parts were breaking. The vehicle no longer starts and had to be taken via flatbed to the dealership where I was informed the engine had to be replaced.

- On 9/23/2025 while driving down the main street, the vehicle unexpectedly shut down (engine stopped running) and would not restart. The vehicle is currently at Elevation GMC (Boone ,NC) waiting to be diagnosed. - Safety was put at risk by the vehicle unexpectedly shutting down in the middle the of rush hour traffic and not being able to be moved. - When it is was towed into the dealership and explained to the service manager what happened; she said "there is a known problem with the gear select lever losing communication with the truck and not knowing what gear it is in". - As of 9/24/2025; dealership has not looked diagnosed what the problem is/was. - There were no prior warning messages before the engine shut down.

I purchased a 2025 GMC Denali a few months ago. At approximately 7,000 miles, the front brakes failed unexpectedly and were replaced by the dealership. However, by 14,000 miles, I began experiencing brake issues again. Before I could return the vehicle for service, I was driving on the turnpike when the engine suddenly seized without warning. This created an extremely dangerous situation—vehicles behind me nearly collided as I lost power and control. I managed to pull over safely, but the tow truck operator struggled to load the vehicle due to all four wheels locking up and the engine being completely seized. Once the vehicle was inspected at the dealership, I was informed that the engine had failed and would need to be replaced. I am aware of the recurring issues associated with the 6.2L GMC engines and related component failures, and I no longer feel safe driving this vehicle. Given the repeated mechanical failures and the serious safety risks involved, I am formally requesting that GMC initiate a buyback of this vehicle. I believe this situation qualifies under lemon law protections and warranty obligations, and I urge GMC to take immediate action to resolve this matter.

I’m filing this safety complaint in addition to a previous complaint, 11678151. which occurred on August 1, 2025. On Friday, August 22, 2025, I experienced a 2nd Traction Control alert and engine failure lights on my 2026 Sierra Denali Ultimate truck which again caused the acceleration to drastically decline while driving home from work. Thank God my kids were not in the car with me this time.  I am extremely appalled and confused as I've NEVER experienced this level of substandard operation from a new vehicle. I have informed the leadership team team at Cavender GMC West San Antonio, TX of the situation. The dealerships recommended (2) paths to exit the vehicle: GMC Customer Assistance and dealership trade-in.

The contact owns a 2025 GMC Sierra 1500. The contact stated that while driving at an undisclosed speed, the vehicle experienced a loss of automotive power. No warning light was illuminated. The vehicle was towed to a local independent mechanic, where it was diagnosed and determined that the engine had seized and needed to be replaced. The local dealer was contacted. The vehicle was not diagnosed or repaired. In addition, the contact related the failure to an unknown recall; however, the VIN was not under recall. The manufacturer was made aware of the failure. The failure mileage was approximately 75,000.

While in the parking lot of a local grocery store, I shifted the vehicle into reverse, at which point all dashboard warning lights immediately illuminated and the braking response became significantly weakened and nearly unresponsive. I placed the vehicle back into park, paused, and then attempted to shift into reverse again, but the dashboard alerts and brake issue persisted. This created a very unsafe driving situation because the brake system was very unresponsive. Despite the unsafe condition, I cautiously drove to my home 2miles away at a speed of under 20 MPH, requiring excessive brake pressure to bring the vehicle to a stop. I parked the vehicle in my driveway and left it there overnight. The next morning, I tested the brakes, and they seemed to return to normal so I drove 5 miles to my local GMC service center. Service Tech confirmed Check Engine Light On and reported code P0700 and P00FF in the report.

The contact owns a 2025 GMC Sierra 1500. The contact stated while driving approximately 4 MPH and turning left into a parking spot, the vehicle independently accelerated. The contact stated that the brake pedal was depressed. The contact stated there was no warning light illuminated. The contact stated that the failure was intermittent, but the failure occurred while slowing down under 5 MPH and turning to the left. The contact had taken the vehicle to a local dealer; however, the failure was not duplicated. The vehicle was not repaired. The manufacturer was informed of the failure. The failure mileage was approximately 17,000.

The vehicle was purchased for the express purpose of towing a 6,600 lbs Travel Trailer. This truck is equipt with the 3 liter Diesel engine. While towing the truck computer counts down milage available based on Def level. The count down is not mile for mile it is an exponential count down. This factor triggers a series of warnings concerning vehicle operation and impending speed restrictions. 1000 mile DEF range warning is first up. Followed shortly there after with a 300 mile DEF range warning (700 miles had never been reached to trigger the warning). The next warning is "DEF Low (red warning) speed restricted soon". Shortly there after a 500 mile count down starts for the first impending speed reduction to 65 MPH max. This is followed by other speed restrictions that will put the vehicle eventually into a 5 MPH speed restricted mode. When adding DEF to the tank the level has never been below 60% full. Its not empty as the gauge and computer indicate. With each filling of the DEF tank the range you can drive is less and less until the truck is driven without the trailer hooked up. GM has a service bulletin for this situation that has been in place since September 23, 2024 and no permanent repair of solution has been prescribed. During the 500 mile count down to the first speed restriction the instrument cluster is locked out to only display "DEF Empty" and alternately the DEF range counting down. No other safety features are visible such as engine temp or transmission temp important to know while towing. I Purchased this vehicle March 17, 2025 stating my intentions to tow a travel trailer. The dealership no GMC ever made me aware of the Service bulletin of the DEF restrictions. Had they done so I would have purchased a different vehicle with out the associated travel issues. Please reference GM Service Bulletin #24-NA-196 Document ID 6736285. This document was given to me after my 4 visit to a GMC dealership to have the issue addressed.