Mileage when the problem started
Owner reports
Selected complaints filed with NHTSA by 2018 GMC Terrain owners, lightly cleaned up (personal details are redacted by NHTSA).
The contact owns a 2018 GMC Terrain Denali. The contact stated while the contact's daughter was driving, the brake pedal was depressed, however the vehicle failed to stop as intended. In addition, the contact stated that the brake pedal was unusually hard when depressed. The vehicle was taken to the dealer where the vehicle was purchased. The contact stated that the service brake vacuum pump failed while the vehicle was at the dealer. The vehicle was diagnosed with a failed service brake vacuum pump and a failed engine. The contact was informed that the service brake vacuum pump, the CAM Shaft and the engine needed to be replaced. The vehicle was repaired. The contact stated that the failure was a known failure of the vehicle. The manufacturer was not made aware of the failure. The failure mileage was approximately 260,000.
The contact owns a 2018 GMC Terrain. The contact stated while driving 40-45 MPH, the vehicle started coasting and stopped unintendedly. The contact stated that the vehicle drove for a while and then coasted and stopped. The message that the "Engine Power Reduced" was displayed. The contact stated that the brake system warning light was also illuminated. The vehicle was towed to an independent mechanic who determined that the camshaft had disintegrated into the engine. The mechanic informed the contact the vehicle was unrepairable. The vehicle was not repaired. The local dealer was not contacted. The manufacturer was not made aware of the issue. The failure mileage was approximately 60,000.
The contact owns a 2018 GMC Terrain. The contact stated that while driving at an undisclosed speed, the vehicle stalled. There was no warning light illuminated. The vehicle was restarted; however, the failure recurred. The vehicle was taken to an independent mechanic where it was diagnosed that the vacuum pump had failed and needed to be replaced. The vehicle was not repaired. The vehicle was taken to the dealer where it was diagnosed that the vacuum pump had failed and needed to be replaced. The vehicle was repaired. The manufacturer was made aware of the failure. The approximate failure mileage was 121,000.
The contact owns a 2018 GMC Terrain. The contact stated while driving at approximately 65 MPH, the check engine warning light illuminated, and the vehicle decelerated to 20 MPH. Additionally, the message "Service Emissions" was displayed. The vehicle was taken to the local dealer who diagnosed that the diesel particulate filter was faulty and needed to be replaced. The vehicle was not yet repaired. The manufacturer was notified of the failure, but no assistance was offered. The contact was informed that the VIN was not included in the Extended Warranty coverage for the repair. The failure mileage was 26,000.
The contact owns a 2018 GMC Terrain. The contact stated that while her husband was driving 30 MPH, the message "Engine Power Reduced" was displayed and the vehicle stalled. The vehicle was not able to be restarted. The contact stated that the vehicle was coasted off to the side of road. The vehicle was towed to the residence and then to a dealer where it was diagnosed and determined that the engine needed to be replaced. The vehicle was not repaired. The manufacturer was notified of the failure. The failure mileage was approximately 92,000.
The contact owns a 2018 GMC Terrain. The contact stated while driving 45-50 MPH, a message indicating that the engine was not at full capacity was displayed. The vehicle was taken to the dealer, where it was diagnosed that the engine had failed and needed to be replaced. The vehicle was not repaired. The manufacturer was not notified of the failure. The failure mileage was approximately 342,000.
My car started experiencing a strange problem while braking on June 15. I released the parking brake leaving my parents driveway. I coasted backwards (as usual), and when I pressed the brake the car didn't stop as expected and the brake pedal was very hard to press. It eventually stopped. I put into park, then put the emergency brake on, then released all and tried again and encountered the same issue, that it was very very slow to stop and the brake pedal was hard to push in. I got home, parked the car - tested the reverse brake on flat surface and didn't notice the issue. The next day, the problem started happening with the front brake as well and an error code popped up that said 'check brake assist' which I've never seen before. …
April 2025, Vacuum Pump went out meaning lost breaks going 60 miles per hour down the road after engine light came on. Left me and two children stranded 2 hours from home with no way to get back except a tow. Now September 2025 Cam Shafts are out as well as Vacuum Pump. Stranded boyfriend and I two hours away again. Now metal in oil and warranty is not willing to cover it due to the vacuum pump going out. Made a post on Facebook and got lots of feedback on how their newer terrains have done the same things. Work in insurance and have people car pertaining to their terrains wondering if we cover engine replacements. There is major issues with these vehicle. Mine only has 107,000 miles on it and I have 12,000 left to pay. The motor is shot and dealership wants to "flush" the metal out of the engine. …
The 2018 GMC Terrain has the AutoStop feature but does not incorporate a switch to defeat AutoStop. In heavy stop and go traffic or when fast acceleration from stop is required, the response of the engine in having to restart creates not only a nuisance condition but a severe accident hazard. It not only hesitates from stopped, it lurches forward after hesitating, which could cause a collision with a vehicle in front. I have had several other vehicles equipped with AutoStop, and all of them have a defeat or cancel AutoStop switch to allow the operator the opportunity to turn AutoStop Off. My 2018 Terrain Denali is now on its third battery. Having a dead battery in traffic also constitutes a safety hazard as does the inherent danger of using jumper cables. I have asked my dealer for a way to defeat the faulty feature, but they either cannot or will not do it. …
Driving 2,5 hrs from Binghamton, NY towards Long Island on Saturday. We took a short break and after that I got onto the highway and not even hit the 50 miles/hour speed I received "engine power reduce" alert on the dashboard and car stalled. I was able to pull the car off the road. I was provided a tow truck by the state police and moved to closest GMC service, GRAND PR ZE GMC Nanuet, NY. This car has only 30,309 miles and it's 2018. The car has been fixed by replacing 5 parts, oxygen sensor, pcv tube, air inlet tube etc. We ended up paying $1,460 just before the Holidays. Rightfully, we are very upset with this unexpected event driving a basically brand new car, in 30000 miles. This car has been mostly driven by my wife who is in 60s in local streets not exposed to harsh enviroments. …
Engine complaints in other Terrain years
Frequently asked questions
How common are engine problems on the 2018 GMC Terrain?
NHTSA has 56 complaints about the engine & cooling of the 2018 GMC Terrain, 25% of the model year's 225 complaints.
Is there a recall for 2018 GMC Terrain engine problems?
No. NHTSA lists no engine & cooling recall for the 2018 GMC Terrain, though it has 5 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 2018 GMC Terrain engine problems start?
Half of the complaints with a recorded mileage happened before about 25,000 miles, and 50% before 25,000 miles.
Is it dangerous?
Owners linked 0 crashes, 1 fire and 0 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.