2020 GMC Terrain Complaints

SERVICE BRAKES — Filed 07/16/2026

I was traveling down the interstate at 70mph. Traffic began slowing ahead of me. I hit the brakes and the pedal was rock hard and I could not stop my vehicle safely. Service brake assist light flashed momentarily. Ended up being the vacuum pump. I was told by the dealership I had it towed to that the vacuum pump had broken off and failed. This was an absolutely horrifying situation that could have caused severe injury or death.

ELECTRICAL SYSTEM,SEATS,UNKNOWN OR OTHER — Filed 07/17/2026

The back passenger seat exploded and caught fire, burning the back of the seat in front and burning the ceilings. Inside the whole vehicle is black from smoke damage. Incident assessed by fire marshal who has ruled as electrical issue. No warning lights or systems displayed anything.

FUEL/PROPULSION SYSTEM — Filed 07/09/2026

Vehicle was filled with a full tank of gas, went to crank the car up to go home from work it acted like it wanted to crank but seemed to be getting no gas. Diagnostic was performed and the fuel pump control module failed. I thank God It did not start because if it did and I just so happen to pull out into traffic and the car just die in the middle of the road I don't think it would of been pretty. Frankly I think it would of be a very dangerous situation. My vehicle was not part of the recall but somehow my vehicle was still affected hopefully GM would look into the 2020 Terrains with the 2.0 engine. Maybe I will be reimbursed.

ENGINE AND ENGINE COOLING — Filed 04/20/2026

See attached document for complaint.

UNKNOWN OR OTHER,BACK OVER PREVENTION — Filed 06/15/2026

Backup camera stopped working and displays a blue screen stating “service backup camera.” This was an issue when the vehicle was under 3 year manufacturer bumper to bumper warranty and was fixed by dealer at no cost. Now this same issue has occurred again approximately 3-4 years later. I thought at first this was an issue specific to my vehicle but now after doing research I see this is an issue across several GMC Terrian vehicles and other GM vehicles. This issue should be fixed by the manufacturer for all vehicles affected. Vehicle owners should not be responsible to fix faulty parts from the manufacturer.

FUEL SYSTEM, GASOLINE — Filed 05/23/2026

The contact owns a 2020 GMC Terrain. The contact stated that shortly after refueling the vehicle, the vehicle suddenly stalled while accelerating from a stop light. The contact stated that after the vehicle stalled, the transmission failed to shift out of park, and the vehicle failed to restart. The vehicle was later towed to the local dealer to be diagnosed. The vehicle was diagnosed with fuel pump failure. The fuel pump was replaced, and the vehicle was repaired. The manufacturer was not yet contacted. The failure mileage was 46,917.

UNKNOWN OR OTHER,SERVICE BRAKES,ENGINE — Filed 06/07/2026

On June 7, 2026, I was driving my 2020 GMC Terrain. I was going at about 40MPH along a very busy main road. While slowing for a red light the Check Engine Light turned on and the car displayed a notice about reduced engine power. Seconds later, the brake pedal became stuck and would not press down all the way and I lost braking ability. The car rattled/shook violently, made a grinding noise, and then the engine shut off and the car stopped abruptly, narrowly avoiding hitting the car in front of us. I turned on the hazard lights. I was not able to get the car to start again, nor was I able to get the car to shift into any other gear including neutral. We were nearly hit by other vehicles multiple times while attempting to get the car to move again, and to get myself and my child safely out of the road. Myself and multiple bystanders attempted to engage the transmission interlock override multiple time. We were eventually able to engage it and push the car to the side of the road. This failure created an extremely unsafe situation for all involved as this road is very busy and there were numerous near-collisions both with my disabled vehicle, and with other drivers serving out of the way and into other lanes at the last second. As time went on and the battery drained, most of the car's exterior lights turned off and other drivers had a hard time seeing my car. I used a strobe flashlight to alert other drivers but this required that I had to stand in the road near the vehicle. Police were called immediately when I found that we could not move the car out of the road, but they did not arrive. Ultimately the vehicle was stuck and inoperable in a travel lane for over two hours. The car was then towed to a nearby repair shop. The mechanic evaluation stated that the brake vacuum pump had failed resulting in loss of braking ability and expensive damage to the engine and other components. The manufacturer is aware of this issue. See: Thieme, et al. v. General Motors LLC.

SERVICE BRAKES — Filed 05/30/2026

The brake vacuum pump had a catastrophic failure which resulted in the immediate loss of all brakes in the vehicle. I had the vehicle repaired only to find that GM has issued numerous repair bulletins to dealers and mechanics. This appears to be an issue known to them. As the vehicle was repaired, the parts are no longer available for inspection. This was a danger to me and others around me because I was traveling 60mph down hill with no means to slow or stop. I narrowly avoided an accident. There were no warning lamps before the incident. A warning lamp did come on after the loss of brakes but only after I attempted to brake.

SERVICE BRAKES,ENGINE — Filed 06/03/2026

During my daily commute to work on the interstate the service break assist message came on my dash and when attempting to break the pedal was very hard, to the point where I had to push extremely hard and quickly realized I had to brake much much soon than normal to prevent hitting other vehicles. Sudden loss of brakes put me and other drivers at risk due to my near inability to slow down or stop and the sudden and unexpected nature of the event.

SERVICE BRAKES,ENGINE — Filed 06/02/2026

I am a [XXX] resident. While commuting to work in [XXX], my GMC Terrain experienced a sudden, catastrophic failure of the brake vacuum pump while traveling at highway speeds. When I attempted to slow down for the exit, the brake pedal instantly became extremely stiff and nearly impossible to depress. I realized I had suffered an absolute loss of power braking assist. To avoid a high-speed collision with heavy highway traffic, I was forced to deliberately steer onto the roadside rumble strips, relying on tire friction to slow the vehicle down. This severe near-miss left me terrified and distraught. Because the shoulder was narrow, my disabled vehicle was left partially protruding into the active roadway. Passing cars sped by so close that my vehicle was violently rocking, creating an incredibly unsafe situation. I was forced to call the State Police for emergency assistance. They dispatched a trooper and a tow truck to remove me and the vehicle safely from the highway. The vehicle was towed to a mechanic in Massachusetts. The mechanic discovered that the vacuum pump had internally exploded. This explosion sent catastrophic metal shards and debris directly into the engines oil galleys and oiling system. While the vehicle has 121,776 miles, this is not a normal wear-and-tear component failure. The brake vacuum pump suffered a catastrophic internal mechanical explosion at highway speeds, completely eliminating my ability to stop the vehicle. A mechanical component failure should never cause an immediate, life-threatening loss of brake control, regardless of mileage. This is a known, systemic engineering defect that is currently the subject of active federal class-action litigation (XXX v. General Motors LLC). This defect did not just cause an immediate life-threatening braking failure, it completely contaminated the oiling system, destroyed the entire engine, and rendered the vehicle a total loss requiring a full engine replacement. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)