2020 GMC Terrain Complaints

SERVICE BRAKES — Filed 09/15/2026

While driving at the speed limit the vacuum pump failed on my 2020 GMC Terrain. This failure led to me enter an intersection with heavy cross traffic, nearly striking g several vehicles. This is the 3rd time I have had to replace this pump in 2 years. The pump explodes sending chards of metal into the engine leading to more damage and labor intensive work.

POWER TRAIN,SERVICE BRAKES,ENGINE — Filed 08/29/2026

While driving my 2020 GMC Terrain, I experienced a sudden loss of normal braking assistance. I had been traveling on the highway and exited onto a main road. As I approached a red traffic light at approximately 50 mph and attempted to brake, the vehicle would not stop normally. I was unable to stop for the red light and went through the intersection before I was able to safely get the vehicle off the roadway. Fortunately, there was no vehicle directly in front of me and I was able to make it through the intersection before any other cars, so no collision occurred. The vehicle was subsequently inspected and diagnosed by a GMC dealership. A diagnostic scan performed after the incident showed code P0556 for the brake booster pressure sensor circuit range/performance. The GMC dealership later diagnosed problems involving the vacuum pump, exhaust camshaft, and timing components and recommended replacement of the vacuum pump, exhaust camshaft, timing components, and related parts.” The sudden loss of braking assistance created a serious safety hazard and could have resulted in a collision, serious injury, or death. The vehicle is currently available for inspection.

POWER TRAIN,ENGINE — Filed 12/17/2021

Having the start stop issue on my terrain and recently over the last few months, it has been using oil everything that sounds exactly like the recall but mine is not included. My start stop is not working and I have to get him since it had only 60,000 miles on it years ago, but nothing was done.

FUEL/PROPULSION SYSTEM — Filed 09/02/2026

Fuel pump control module and or the in tank fuel pump failed and or isn’t making proper connection for car to run correctly. Safety was put at risk as car came to abrupt halt while driving. Driver was outside of vehicle at busy intersection for vehicle diagnostics and battery jump. Battery was removed and new battery installed yet problem persists. Not confirmed by dealer but code is as follows (p129F). Maintenance performed by owner;Code reader used for diagnostics, new battery installed. Problem persists. Car started, drove and stumbled to then die. Check engine now displays.

SERVICE BRAKES, HYDRAULIC — Filed 08/24/2026

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.

FUEL/PROPULSION SYSTEM — Filed 08/19/2026

COMPONENT OR SYSTEM FAILED - GMC Dealership replacing fuel pump. SAFETY OR SAFETY OF OTHERS AT RISK - stalled in remote area with no internet/cell service. In order to get to safety we travelled 13 miles of narrow 2 lane roads with no shoulder or escape areas. Road included 3 miles of a steep downhill grade. HAS THE PROBLEM BEEN REPRODUCED OR CONFIRMED BY A DEALER - Yes, Walser GMC [XXX] WERE THERE ANY WARNING LAMPS, MESSAGES OR OTHER SYMPTOMS OF THE PROBLEM PRIOR TO THE FAILURE - No, drove 400 miles w/2 stops, rest stop and lunch/gas. Got to our destination, shut off the car. Needed to move the vehicle to designated parking spot and at first the vehicle would not start, got it started but lurched forward, engine chugged, no acceleration and then stalled. Waited 10 minutes vehicle started with same symptoms but became drivable so we headed to safety 13 mile to nearest town, [XXX]. The area has recently been battling forest fires and in our area, although "safe", there was still HIGH fire danger. We did not feel safe w/o a vehicle for (possible) rapid escape. The city has limited services, no rental car company, no Uber/Lift, closest car dealership 90 miles away. Vacation cancelled. Hired North [XXX] Towing to transport vehicle and people 300 miles to Walser [XXX], [XXX]. Family member drove us to our home in [XXX]. To date vehicle mileage - 30,000 miles! INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

SERVICE BRAKES — Filed 08/23/2026

The brake suddenly became impossible to depress more than 3/4 of an inch. Almost unable to stop nearly hitting another vehicle. The dashboard then lit up with a "service brake system" warning. Luckily was only a few minutes from home brought it home and began the search for the issue. The brake vacuum pump failed. Unsure of further damage at this point. It being Sunday am unable to contact a shop or dealer.

SERVICE BRAKES,ENGINE — Filed 08/19/2026

While driving, I suddenly smelled something burning. Immediately after, a warning popped up stating 'Engine power is reducing,' the check engine light came on, and I experienced a sudden, near-total loss of power braking assist, making the brake pedal extremely hard to press. I had to use intense force to bring the vehicle to a stop. A scan of the vehicle's OBD-II codes revealed codes P0556 (Brake Booster Pressure Sensor Circuit), P0014 (Exhaust Camshaft Position Timing Over-Advanced), and P0017 (Crankshaft Position - Camshaft Position Correlation). This is a known failure where the engine-driven mechanical brake vacuum pump seizes up, destroys the braking vacuum assist, and bends or shifts the exhaust camshaft reluctor wheel, causing a severe and immediate safety hazard while in motion.

UNKNOWN OR OTHER — Filed 08/06/2026

During heavy rain, the sunroof on my Terrain leaked badly enough to allow a substantial amount of water into the vehicle. The rear floor area became completely saturated, and the sunroof controls stopped working. I brought the vehicle to Hudson Cadillac Buick GMC in Poughkeepsie, New York, to have the problem diagnosed and repaired. The resulting repairs and water-damage cleanup cost me nearly $3,000 out of pocket. I was advised that the damage was not covered by my warranty or by my insurance. What concerns me most, however, is that this does not appear to have been an isolated incident. While my Terrain was at the dealership, I learned that four other GMC Terrains were also at the dealership experiencing water damage related to leaking sunroofs. Mine was the fifth. Finding five Terrains at the same dealership with what appeared to be similar water-intrusion problems was extremely concerning to me and made me question whether this is a recurring issue with these vehicles. I also have a video provided by the dealership documenting the water damage to my vehicle, and I am happy to provide that video, my repair invoice, photographs, or any other documentation you would like to review. They went to great lengths to dry the vehicle, which was especially important to me because I was extremely concerned about hidden moisture and dangerous mold. Thankfully, after their work, there is no odor and no indication of remaining moisture or mold, and I am very satisfied with the quality of the repair and cleanup. The extent of the water damage was frightening. At one point, I was genuinely concerned that I might have to get rid of the vehicle simply because I was afraid of the long-term consequences of having so much water inside it. I am very grateful that the dealership was able to restore the vehicle so thoroughly but there is still a possibility that the repair will fail and I will have to replace the sunroof module.

FUEL/PROPULSION SYSTEM — Filed 07/25/2026

While driving home from work my 2020 GMC Terrain stalled and turned off. I was on a very busy 2 lane road, crossing a intersection in a tourist area in [XXX]. This could have be come fatal very easily. I was able to get the car started and Home but had to take it very slow. Next day we weren't able to get the car started nor turned on. Battery is new and still works, we also had a mechanic come to the house and run his computer telling us it was the Fuel Pump Control Module. There were no warning signs leading up to this moment. I see there has been recalls for the same issue for 2021 and 2022 models but my GMC dealership I bought my car at is telling this isn't an issue in any Terrain that they are aware of. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

UNKNOWN OR OTHER — Filed 08/06/2026

When the gas is mashed to accelerate, the car does not want to go. It has left me stranded and rolling in the middle of traffic. I am scared to drive it.

POWER TRAIN,FUEL/PROPULSION SYSTEM — Filed 07/30/2026

Because of the intentional failure of GMC and there promise of “We are Professional Grade”, I almost got plowed down by a semi when the car began to quit on the highway going 60. After pulling into the next driveway, which happened to be a Parker’s Kitchen, and ending up on the curb spot, thanking God I wasn’t dead, I sat there for a moment wondering what just happened. As I went to restart the car, it wasn’t having any of it. 40,000 miles, not professional grade GMC, circus grade. Towed it to my home, figuring it has to be something minor and a diy fix. Bought the hyper-tough code reader delivered by Walmart and it delivered professional grade results: U18A2, P1787 and P187E. I am beyond pissed. I could have died due to your intentional negligence in manufacturing. I have a car that will not start, with payments. I have searched the internet and found your “save ourselves plan” and let’s do a voluntary recall starting with 2021 on the same failed parts I am dealing with at the moment. Thanks GMC, who is the ringleader of your circus?

SERVICE BRAKES — Filed 07/20/2026

While driving north in interstate 79, the brakes became very hard to push making it difficult to stop the vehicle. We got off the interstate and proceeded back home. The brakes were as hard as a rock to push and it was difficult to stop the vehicle. When this happened, the check engine light came on and stayed on. It was very dangerous to drive due to the brakes not working properly and the stopping distance was greatly reduced and it was difficult to stop the vehicle putting our family at risk for their safety. We took the vehicle to a repair shop and they checked and diagnosed the issue and told us the vacuum pump for the brakes was no good and needed replaced. We found that this is a common issue for breakdown on our type of vehicle. Repairs were made and the total cost was $352.24 including tax.

SERVICE BRAKES,ENGINE — Filed 07/09/2026

Vacuum pump failure causing sudden and unexpected hard brake pedal and loss of braking coming off the highway. Ended up catastrophic engine failure. This is the SECOND incident with this vehicle of the exact same problem. GMC refuses to address this issue and continues to risk the lives of their customers.

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.

SERVICE BRAKES — Filed 03/03/2025

SERVICE BRAKE ASSIST CAME ON, CHECK ENGINE LIGHT CAME ON AND VEHICLE WAS HARD TO STOP. Took to authorized service dealer and all parts were replaced. After driving it for a little while, SERVICE BRAKE ASSIST BACK ON, CHECK ENGINE LIGHT BACK ON AND VEHILCE IS HARD TO STOP.

SERVICE BRAKES — Filed 09/16/2025

My 2020 GMC Terrain brakes pump failed causing me to hit the median wall on the highway.

Carry Handle, Shell, Base — Filed 05/16/2025

During a vehicle accident, my 2.5 year old daughter's car seat detached from the base and landed in the back part of my part. We were t-boned on the passenger side back seat. We spun and the car seat detached and she was flung around the car. She had severe whiplash, a contusion and possible fabric burn on her head. She was buckled in properly and the car seat was properly installed. Yes, all parties (other than manufacturer) saw and inspected the car seat.

SERVICE BRAKES,FORWARD COLLISION AVOIDANCE — Filed 12/26/2024

The brake system failed. No warning. When the brakes failed, driver ran the car into a tree to stop instead of hitting pedestrians or other vehicles

VISIBILITY,STRUCTURE — Filed 10/10/2023

The contact owns a 2020 GMC Terrain. The contact stated that rain water had leaked from the sunroof drainage into the vehicle causing the floor carpets to become saturated with water and mold had developed inside the vehicle. The contact also discovered a pool of water inside the spare tire well. The vehicle was taken to the local dealer who replaced the sunroof motor and sunroof liner, unclogged the sunroof drainage assembly and replaced the carpets. The contact indicated that later the failure had reoccurred although the sunroof drainage assembly was consistently unclogged each time the vehicle was in for service. The contact had also experienced respiratory illness due to the mold present inside the vehicle. The manufacturer was notified of the failure but no assistance was offered. The failure mileage was 12,300.

SERVICE BRAKES — Filed 09/09/2023

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

VEHICLE SPEED CONTROL,SERVICE BRAKES,ENGINE — Filed 08/06/2023

While on highway service brake system warning light came on,brake became hard to apply almost causing an accident. Vehicle had to be towed to a repair shop(dealer).after paying over $1600 the problem was not resolved and found there are numerous complaints about issues with the terrain and no recall issued.are they waiting til someone dies before a recall?

UNKNOWN OR OTHER — Filed 06/04/2023

I was driving approximately 75mph on the interstate. 3 hrs into my trip I started feeling hot so I turned the a/c up. In my peripheral vision I saw orange and thought a car was beside me on fire. Immediately I realized it was my vehicle. I immediately slowed and came to a stop. I put it in park and opened the door. By the time I started to exit there were flames higher than the rear windows. A car that was behind me stopped. They said about a mile back there was a spark under the car by the rear tire. Then it went up in flames.

FORWARD COLLISION AVOIDANCE — Filed 07/27/2022

The emergency breaking system failed to engage. Failure to engage caused collision with another car

WHEELS,SERVICE BRAKES — Filed 09/18/2020

WHEN REVERSING OUT OF A PARKING SPOT, BRAKES FAILED CAUSING ACCIDENT. MULTIPLE ATTEMPTS TO DEPRESS BRAKE PEDAL WITH NO BRAKING. HIT A PARKED CAR. AFTER SHUTTING CAR OFF AND ATTEMPTING TO MOVE VEHICLE BRAKES DID ENGAGE AND RESPOND CORRECTLY. REAR DAMAGE TO TERRAIN OCCURRED REQUIRING TOWING.