Mileage when the problem started
Owner reports
Selected complaints filed with NHTSA by 2020 GMC Terrain owners, lightly cleaned up (personal details are redacted by NHTSA).
The contact owns a 2020 GMC Terrain. The contact stated that while driving 50 MPH, the vehicle lost braking power. The driver was able to pull over safely. There were no warning lights illuminated. The vehicle was towed to the local dealer, where it was diagnosed that the vacuum pump had shattered. The vehicle was repaired, but the failure recurred. The contact reached out to a GMC engineer, who informed the contact that the failure was due to the camshaft reluctor. While driving, the vehicle lost engine power. The vehicle was towed to the same local dealer, where it was diagnosed that the throttle body needed to be replaced. The vehicle was repaired, but the failure recurred. The vehicle was towed to the local dealer, where it was diagnosed that the turbo code had a mass air flow sensor failure. The vehicle was repaired. …
The contact owns a 2020 GMC Terrain. The contact stated that while driving at slow speeds in a parking area and attempting to stop, the brake pedal failed to depress all the way to the floorboard and was firm, requiring an increased effort; however, the vehicle failed to stop as intended. The contact was able to bring the vehicle to a complete stop by turning the vehicle off. No warning lights were illuminated. The vehicle was taken to the dealer, who diagnosed a failure with the brake vacuum pump, observing that the pump had sent metal fragments into the engine, resulting in damages to the engine. The vehicle was not repaired. After investigating the failure, the contact related the failure to Special Coverage Adjustment: N182202780. The manufacturer was notified of the failure, and a case was opened. The failure mileage was 108,000. The VIN was not available.
The contact owns a 2020 GMC Terrain. The contact stated that the vehicle failed to stop while driving 55 MPH while depressing the brake pedal. The contact pressed the button that immediately shifted the transmission to park, and the vehicle came to a stop. The contact drove the vehicle to a safe parking space. After safely parking the vehicle off-road, the check engine and brake assist warning lights illuminated. The vehicle was towed to the dealer who diagnosed that the brake booster pump and camshaft had fractured and detached from the vehicle. The contact was informed that the brake booster, vacuum pump, and camshaft needed to be replaced. The vehicle was not repaired because the dealer was awaiting the parts to repair the vehicle. The manufacturer was not informed of the failure. The failure mileage was 101,700.
The contact owns a 2020 GMC Terrain. While the contact's wife was driving approximately 40 MPH and attempting to depress the brake pedal to pull into the parking lot of Walmart, the braking distance was extended while bringing the vehicle to a complete stop. The driver used excessive force on the brake pedal using both feet. The vehicle was towed to a certified mechanic, who diagnosed the vehicle and determined that the brake vacuum pump had failed. The vacuum pump had fractured where it was connected to the camshaft, causing pieces to enter the engine. The brake vacuum pump and the connector were replaced. The manufacturer was made aware of the failure. The failure mileage was approximately 156,000.
The contact owns a 2020 GMC Terrain. The contact stated while driving 20 MPH, while attempting to slow down, the brake pedal was depressed; however, the brake pedal felt abnormally stiff. In addition, the vehicle hesitated to come to a complete stop. The contact became aware that the driver's side and passenger's side struts had failed. The check engine warning light was illuminated. The vehicle was taken to the dealer where it was diagnosed that the brake vacuum pump needed to be replaced. The brake vacuum pump was replaced, and the vehicle was repaired. The manufacturer was notified of the failure and referred the contact to the dealer for assistance. The approximate failure mileage was 17,361.
The contact owns a 2020 GMC Terrain. The contact stated while driving 40 MPH the "Brake Assist" warning light illuminated. The contact attempted to depress the brake pedal, but the pedal was stiff. The contact was unable to depress the pedal. The vehicle was taken to a local dealer and unknown repairs were performed. The vehicle was repaired; however, recently the failure reoccurred. The contact stated that the "Brake Assist" warning light illuminated, and the brake pedal was difficult to depress. The vehicle was not taken to a dealer or an independent mechanic to be diagnosed or repaired. The manufacturer was not informed of the failure. The failure mileage was approximately 162,000.
Driving down the freeway and all of a sudden got a service break assist notification and without warning I was unable to stop the vehicle. I was able to coast my way off the freeway and upon my exit I tried to pull into an empty parking lot but there was a fire fence I ended up crashing into which is probably what brought the vehicle to a complete stop. This is very dangerous and I have read numerous complaints from other 2020 terrain owners who have experienced the same problem. Mechanic stated I need need vacuum pump for brake booster which of course my warranty doesn't cover. Something seriously needs to be done about this. My accident could have been a lot worse
The contact owns a 2020 GMC Terrain. The contact stated that while driving up the driveway at approximately 10 MPH, the brake pedal was depressed but failed to function as intended. The contact used force to depress the brake pedal. When the vehicle came to a stop, there was an abnormal grinding sound coming from the front brakes. The contact stated that the message "Power Assist Brakes" was displayed on the instrument panel. The vehicle was not taken to the dealer or an independent mechanic. The vehicle was not repaired. The manufacturer was not made aware of the failure. The failure mileage was approximately 198,000.
The contact owns a 2020 GMC Terrain. The contact stated that while driving at an undisclosed speed, the vehicle failed to stop as intended. The brake pedal was depressed to the floor, and the vehicle slowed down and eventually stopped. The vehicle was taken to an independent mechanic, where it was diagnosed with a failed vacuum pump. The mechanic informed the contact that the vacuum pump needed to be replaced. The vehicle was repaired. The contact stated that the failure was a known issue with the vehicle. The manufacturer was not notified of the failure. The failure mileage was approximately 92,000.
The contact owns a 2020 GMC Terrain. The contact stated while driving at various speeds, the vehicle lost brake functionality while depressing the brake pedal. The contact stated no warning light was illuminated. The vehicle was towed to a local dealer where it was diagnosed with needing the vacuum pump replaced. The vehicle was repaired however, the failure persisted. The manufacturer was not informed of the failure. The failure mileage was approximately 40,000. The VIN was unavailable.
Brake complaints in other Terrain years
Frequently asked questions
How common are brake problems on the 2020 GMC Terrain?
NHTSA has 72 complaints about the brakes of the 2020 GMC Terrain, 37% of the model year's 197 complaints.
Is there a recall for 2020 GMC Terrain brake problems?
No. NHTSA lists no brakes recall for the 2020 GMC Terrain, though it has 2 recalls for other components. If the problem is widespread, a repair may still be covered by an extended warranty or a manufacturer service bulletin — ask a dealer.
At what mileage do 2020 GMC Terrain brake problems start?
Half of the complaints with a recorded mileage happened before about 92,000 miles, and 18% before 25,000 miles.
Is it dangerous?
Owners linked 5 crashes, 0 fires and 2 injuries to brakes problems on this model year. If you notice symptoms, have the car checked before driving further.
Source: U.S. National Highway Traffic Safety Administration (NHTSA) — owner complaints through October 20, 2026, recalls and defect investigations; fuel economy from the EPA. Complaints are unverified reports and are not proof of a defect. How we rate model years.