SERVICE BRAKES07/12/2026
Vacuum pump failure caused my brakes to lock up and almost caused me to wreck into another vehicle
SERVICE BRAKES07/01/2026
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.
SERVICE BRAKES07/01/2026
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 to: 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
POWER TRAIN04/29/2026
Automatic transmission solenoid control valve body got stuck open and ruined the whole transmission. This has been a reoccurring problem with these vehicles. Image is from a code read. Issue was confirmed by Gastorf Chevrolet, and an independent transmission shop.
ENGINE03/16/2026
The contact owns a 2021 GMC Terrain. The contact stated that while driving at various speeds, the vehicle hesitated while depressing the accelerator pedal, with a misfire coming from the engine. During the failure, the message "Engine Power Reduced" was displayed on the instrument panel. The vehicle was taken to a local dealer, and the contact was provided an estimate for a diagnostic test. The contact declined. The vehicle was not repaired. The manufacturer was not contacted. The failure mileage was unknown.
ENGINE,ENGINE AND ENGINE COOLING03/16/2026
Vehicle went into reduce engine power mode and check engine light came on. Vehicle has just over 60,000 miles. Code is telling me I need a new turbo and being quoted 1,500-3,000. I have read so many people having the same issue with needing a new turbo just after 60,000 miles
ENGINE,FUEL/PROPULSION SYSTEM,LANE DEPARTURE01/26/2026
The engine light came on while driving, saying “engine power reduced”. It barely accelerates, RPMs go over 5, it chugs when driving. Taken to an independent service center.
ENGINE01/22/2026
around chirstmas, Was driving on the highway and the car threw a "reduced engine power" warning and went into limp mode. Check engine light came on. Car asymptomatic prior. got the code pulled and it said turbocharger under boost. The next day the check engine light went out and car was running appropriately. Took the car on the highway again and the car threw the "reduced engine power" warning and went into limp mode again in the middle of freeway traffic. It is a safety concern due to the engine going into limp mode in the middle of high speed traffic. I easily couldve caused an accident putting both myself and others in danger by the engine cutting the power in the middle of the freeway. The check engine light only comes on while going at freeway speeds. The light will then go out overnight and come back on the next time i go back on the freeway at 70-80mph speeds. I have taken it to one shop which reported an oil leak coming from the turbo both inside and outside and that it needed to be replaced. I have read several different forums of other users of the same year, make, and model experiencing the same issue. the car is only a few years old and the likelihood of a turbocharger being bad is uncommon but a major safety concern considering this happened out of nowhere with no signs or symptoms leading up to this.
CHILD SEAT10/31/2025
The contact owns a 2021 GMC Terrain. The contact received notification of NHTSA Campaign Number: 23V339000 (Child Seat); however, the part to do the recall repair was unavailable. The contact stated that the manufacturer had exceeded a reasonable amount of time for the recall repair. The dealer was contacted and informed the contact that the vehicle would not be inspected or repaired. The manufacturer was made aware of the issue. The contact had not experienced a failure.
POWER TRAIN,SERVICE BRAKES,ENGINE AND ENGINE COOLING09/17/2025
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.
UNKNOWN OR OTHER08/03/2025
Constantly have water leaking into spare tire compartment, back seat floors and passenger floor. Mold/mildew smell coming through vents. Have had drains lines cleaned out, and still recurring having this issue. Unknown where leak is coming from. This is a serious health risk.
ELECTRICAL SYSTEM,FORWARD COLLISION AVOIDANCE07/01/2025
Driving my vehicle with no warnings, messages, or symptoms on adaptive cruise control Sunday [XXX] on [XXX] in Michigan. I changed lanes into the right lane when the vehicle abruptly, without notification, and with force, caused braking that unexpectedly and dangerously slowed the vehicle then released braking before doing the same a moment later. Vehicle was pulled off the road onto the shoulder without an accident, thankfully nobody was behind because they would not have been able to stop in time before hitting my vehicle and I assume the brake lights weren't activated since I did not press the brake pedal either time the vehicle was abruptly slowed causing audible noise of traction loss due to skidding. Vehicle engine would function but parking brake remained active leaving vehicle unable to change gears and transmission warning showed on instrument panel. Vehicle towed to a Chevrolet dealer in Grayling, Michigan where it remains and would be available for inspection. Dealer shows transmission as the cause and in need of replacement. Vehicle has been maintained at GM shops since original ownership. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)
Showing 12 of 34 complaints.