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 his daughter was driving at an undisclosed speed, an unknown warning light displayed on the instrument panel. The vehicle started losing motive power and the vehicle shut off while in a parking lot. The contact was notified of the failure and a tow truck was contacted. While waiting for the tow truck to arrive, the contact's daughter was able to restart the vehicle and drive to the residence. The dealer was notified of the failure the following day and the vehicle was towed to the dealer. The contact stated that a diagnostic test was performed, and the contact was informed that metal shavings were found inside the engine and the vehicle was diagnosed with engine failure. The manufacturer was notified of the failure but offered no assistance. The contact was referred to the NHTSA Hotline to report the failure. …
The contact's friend's son owns a 2020 GMC Terrain. The contact stated that while her friend was driving at an undisclosed speed, the brake pedal went to the floorboard while depressed. The brakes failed to immediately stop the vehicle. Additionally, the vehicle made grinding sounds while driving. The vehicle was taken to the dealer, where the vacuum pump, exhaust camshaft, and valve cover gasket were replaced; however, the vehicle lost motive power while driving. The vehicle was towed back to the dealer, where it was determined that the engine needed to be replaced. The vehicle was not repaired. The manufacturer was made aware of the failure and informed the contact that there was no recall associated with the VIN. The failure mileage was approximately 48,552. The contact stated that additionally, the check engine light came on without cause. …
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. The contact stated that the vehicle was taken to a dealer for an oil change. The contact stated that approximately 5 weeks after returning the oil change, while driving at approximately 65 MPH, the vehicle and steering wheel started shaking abnormally and the vehicle lost motive power. The contact stated that the traction control, check engine, and stabili-trak control warning lights were illuminated. The vehicle was taken to a dealer where it was diagnosed that there was no oil in the engine and the spark plugs and ignition coils needed to be replaced. The vehicle was repaired; however, the failure reoccurred three weeks later. The manufacturer was not notified of the failure. The failure mileage was approximately 37,000.
The contact owns a 2020 GMC Terrain. The contact stated while driving at an undisclosed speed, the vehicle lost motive power with the check engine warning light illuminated. The vehicle was towed to an independent mechanic, where it was diagnosed that the fuel pump control module had failed and needed to be replaced. The vehicle was not repaired. The dealer was contacted. The vehicle was not diagnosed or repaired. The manufacturer was not made aware of the failure and referred the contact to the NHTSA Hotline for assistance. The approximate failure mileage was 88,000. The VIN was not available.
As I was driving down the Ohio Turnpike on my way to work on Tuesday, August 5, 2025, my check engine light came on. Almost immediately I got a notification that the car was operating at reduced power. I had no previous issues with the vehicle. As I got off the turnpike my braking system failed. I was able to come to a stop partially in the grass before entering into oncoming traffic. The entire car shut down. I was unable to restart the car. We were also unable to put the car into neutral to push it off of the road the remainder of the way because the wheels were completely locked up at this point. The parking brake was engaged on its own. We also could not get the car into neutral. I had the car towed to a local repair shop, not knowing at all what the issue was. The vacuum pump had failed and broke apart in the engine. This caused my braking system to fail completely also. …
From a complete stop my car refused to accelerate no matter how much I pushed the gas pedal. I was pulling into traffic and was on a hill so my car rolled forward naturally into the road but would not respond to the gas pedal. The RPMs didn't move, the car had power, I tried putting it in reverse and then back into drive. Nothing worked for a solid 2 minutes at least. Then all of a sudden it registered and worked. I was almost t-boned from a car coming through the curve but luckily, they were able to go around me in time. This put me and my small daughter at risk of being severely injured from a malfunction that I can't recreate to show the technicians. Since this incident, it has happened several times randomly. Sometimes I'm at a red light, or backing out of a parking spot, or pulling out into traffic. …
This message concerns a persistent engine light that activates and generates engine code P0299, indicating an engine underboost issue. There have been several occasions where I am driving over 55mph on the highway and my 2020 Terrain SLT fails to pick up speed over 60mph in traffic. I took it to my GMC dealer earlier this year for them to diagnose, and they discovered that the charge air cooler tube had collected moisture. Once that was fixed, the vehicle was fine for about a month when the same thing happened. I took it to another GMC dealer and found that the turbocharger wastegate actuator had to be replaced. Once replaced, I had no problems until it began to get cold where I live. Now the vehicle is doing the same thing. Now what happens is the engine light will come on and give the engine underboost message but goes away after a week of driving. …
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. …
Engine complaints in other Terrain years
Frequently asked questions
How common are engine problems on the 2020 GMC Terrain?
NHTSA has 61 complaints about the engine & cooling of the 2020 GMC Terrain, 31% of the model year's 197 complaints.
Is there a recall for 2020 GMC Terrain engine problems?
No. NHTSA lists no engine & cooling 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 engine problems start?
Half of the complaints with a recorded mileage happened before about 67,000 miles.
Is it dangerous?
Owners linked 0 crashes, 0 fires and 2 injuries to engine & cooling 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.