2025 GMC Sierra 1500

Turned on vehicle and an alert popped up "Brake system control module malfunction", limited speed to 43 miles per hour, no power breaks worked. I have had no issues with brake system for the first 11k miles. I contacted my local GMC dealership (Banks Chevrolette in Concord, NH) and was told that I would not be able to get an appointment until the 2nd week of November. I told them this was a break system issue covered under warranty and they told me I was welcome to DRIVE to their dealership (14 mi away on INTERSTATES and CITY STREETS) and wait to see if there was any time to plug it in, but they would not guarantee there would be time on their end. I spoke with the service manager and was told the same and that his advice was to "not drive it until November". I was able to take the truck to a shop in town 2 mi away , and they printed off the following codes: P25A U160F U1610 U2418 U2419

I was driving in town when all lights on the dash lit up, and I mean all of them. I was approaching a traffic light in low traffic in the 20-30mpg range. I went to apply the brakes and almost had none. If I was going to estimate how much braking was available, it would be in the 10% range. I drove at 20mph to the nearest dealer. They verified the issues. They reflashed the computer, drove the truck afterwards, and pumped the brakes. They told me they recommended an immediate master cylinder replacement. They had seen this twice already in the month of August. Both times prior to mine the reflash initially worked, but the problem returned within a week, and the master cylinders had to be replaced. The master cylinder replacement was a $2600 repair.

On [XXX], while driving my 2025 GMC Sierra 1500, VIN [XXX], near [XXX], California, the vehicle suddenly experienced a severe brake failure while traveling on a public roadway. When I attempted to apply the brake pedal, the vehicle failed to brake normally and I was unable to safely stop the truck using normal braking. I was forced to reduce speed and allow the vehicle to coast until I was able to enter a side road and bring the vehicle to a stop. I was extremely fortunate that traffic conditions were light at the time. A vehicle traveling in front of me, an intersection, pedestrians, or heavier traffic could have resulted in a serious or fatal crash. After stopping the vehicle, I discovered a metal retaining ring/clip on the floor directly underneath the brake pedal area. At approximately the same time, multiple brake system failure and warning indicators illuminated on the instrument panel. I immediately contacted GMC through the vehicle's SOS system and reported the brake failure. The vehicle was subsequently towed and delivered to a GMC dealership/service department for diagnosis and repair. This appears to involve the mechanical separation or detachment of a component associated with the brake pedal assembly. I have retained the metal component, video evidence of the condition and warning lights, towing information, and dealership repair documentation. A sudden loss of braking caused by the separation of a brake pedal component presents an immediate and potentially life-threatening safety risk. I respectfully request that NHTSA investigate this failure and determine whether similar failures have occurred in other 2025 GMC Sierra 1500 vehicles. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

I stopped at a stoplight and my truck shut off, the doors unlocked and then immediately restarted and then came up with a bunch of errors telling me that my brake system failed and to get the traction control serviced. I then had no power braking. This is the second time my truck has shut off at a light and restarted, but I don’t lose my brakes the first time.

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.

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.