general problems of the 2021 GMC Terrain

Driving on the garden state parkway on Sunday night June 28, 2026 I proceed to cross over the ratitan bridge. There was traffic as I was going down the bridge at 70 miles an hour. When I applied the brakes the car would not stop. I had two 6 years old in the backseat. I applied 2 feet to the brake pedal and it was like a rock and the car would not slow down. I thought I was going to crash. I had to steer and lane change several times to avoid hitting other cars. This has something to do with the driving assist braking system. I was scared to death. If this isn’t a safety concern nothing is. This should be a recall for GMC to fix because it’s an accident waiting to happen.

Formal safety complaint – 2021 GMC Terrain brake failure vehicle: 2021 GMC Terrain incident location: garden state parkway (NJ) speed: approximately 65 mph incident description while driving northbound at highway speed, I attempted to change lanes and apply my brakes. When I pressed the brake pedal, it became completely rigid (rock hard) and failed to function. I had no ability to slow the vehicle using normal braking. At that moment, I was forced navigate multiple emergency lane changes to avoid striking other vehicles prepare for potential collision due to lack of braking control apply extreme force with both feet on the brake pedal in an attempt to generate any slowing eventually, I was able to steer the vehicle to the shoulder while exerting maximum pressure on the brake pedal. During the incident, a “driving assist brake” message appeared on the dashboard, and the braking system has remained in this same compromised condition since. Safety concerns the brake pedal became non-functional without warning the failure occurred at highway speed, creating an immediate life-threatening situation this was not a gradual degradation—this was a sudden, complete loss of braking capability the issue persisted after the vehicle was stopped broader concern I have since found multiple reports and videos of other GMC Terrain owners experiencing the exact same failure, suggesting a potential systemic or design-related issue. Given: the severity of braking system failure the apparent repeat nature of this issue the lack of an active recall addressing it I believe this represents a significant safety risk to GMC Terrain drivers and the public. Impact this incident caused: immediate danger to my life and other drivers extreme emotional distress loss of confidence in the safety of the vehicle requested action I am requesting: a formal investigation into this braking failure immediate inspection and repair of my vehicle at no cost clarification from GMC regarding know.

The contact owns a 2021 GMC Terrain. The contact stated that the transmission was previously replaced. The contact stated that upon starting the vehicle, the check engine warning light illuminated. The failure had occurred intermittently. Additionally, the contact stated that while driving approximately 15-20 mph and depressing the accelerator pedal, the vehicle failed to respond for approximately 1 minute. The vehicle was taken to the Nissan dealer it was purchased several times. The dealer retrieved diagnostic trouble codes: p057c and p057e, and the brake pedal position sensor was replaced twice; however, the failure persisted. The Nissan dealer took the vehicle to a gm dealer, where the cause of the failure could not be determined. The vehicle was not repaired. The contact related the failure to TSB number: pit5994 (diagnostic tip for reduced or low engine power on acceleration). The manufacturer was notified of the failure and referred the contact to the NHTSA hotline for assistance. The failure mileage was approximately 78,843.

The contact owned a 2021 GMC Terrain. The contact stated while driving at an undisclosed speed, the brake pedal depressed, and the accelerator pedal was applied with no warning lights illuminated. The contact stated due to this failure the contact collided with and rear-ended another vehicle. The contact stated the airbag did deploy during the accident. The contact stated no medical attention was provided, but the contact suffered bruises from the airbag and seat belt. A police report was filed with the local michigan sheriff's office and the report number was provided to the contact. The vehicle was towed to an independent mechanic. The dealer was not contacted. The vehicle was not diagnosed or repaired. The manufacturer was not made aware of the failure. The failure mileage was not available.

Automatic emergency brakes have unnecessarily or prematurely activated on 2 separate occasions causing my car to stop very abruptly which has resulted in neck, shoulder and back pain. I have been very lucky in the recent past and today that a vehicle was not directly behind me. The seat vibrated first when it sensed the car ahead was breaking. When I started to break, the emergency break kicked in. I did not report this the first time because I thought the car was doing what it was supposed to do. Today was unnecessary. No accident and no police report. I do plan on telling the dealership.

Recently I have noticed that the back brakes squeak and sound like they are grinding when backing up. Also every now and then the information screen will go black for a while then turn back on could be a few seconds or several minutes. 23,900 on car.

When car has been unused for a period of time, the right rear brake makes noise when the car is moved. This happend in either forward or reverse. Even after driving for a short period of time, the noise is still evident. Under warrenty, I asked the dealership to resolve. They indicate this is an ongoing investigation by gm. I purchased the car new in July 2021. This problem has persisted since purchase. I have reported it multiple times to the dealer but they pass it off as gms problem. In reviewing other similar complaints for the 2020 model, it was resolved by changing the brake pads to a different material. Surely gm can find a cure after 3 years since production.