2018 GMC Terrain engine problems

ENGINE

While driving my 2018 GMC Terrain, the vehicle suddenly displayed an “Engine Power Reduced” warning and the brakes became extremely hard to press. The vehicle experienced a sudden loss of normal power-brake assist while it was in motion, creating a serious safety risk because significantly greater pedal force was required to stop the vehicle. I was able to pull over safely. After stopping, the vehicle would crank but would not start. The vehicle was towed to a GMC dealership for inspection. The dealership documented that the vehicle had a suspected failed/broken vacuum pump, a damaged exhaust camshaft, and a damaged exhaust camshaft actuator. The dealership subsequently documented that the engine was severely sludged and stated that the sludge caused the vacuum pump to fail, which then caused the exhaust camshaft to twist and damage the exhaust camshaft actuator. The dealership’s written diagnosis recommends replacement of the exhaust camshaft, exhaust camshaft actuator, vacuum pump, and associated one-time-use parts. The dealership has also documented diagnostic trouble codes P0014 and P0017. The failed vacuum pump and related components should be available for inspection upon request. The vehicle has been inspected by a GMC dealership, which has documented the suspected vacuum pump failure and resulting engine damage. The sudden loss of power-brake assist occurred while the vehicle was being driven and created a potentially dangerous loss of braking capability. I am reporting this because I believe the failure of the vacuum pump and resulting loss of brake assist may represent a safety-related defect requiring investigation, particularly because the vehicle experienced a hard brake pedal without prior warning.

NHTSA complaint #11755920 — an unverified report by a vehicle owner.

ENGINE

The vehicle has had regular maintenance, oil change, and inspection including the brakes. My boyfriend is visiting me in [XXX] from the [XXX]. OnXXX while driving the vehicle the engine started. Making a ticking noise especially during idle and when accelerating in idle. About 15 minutes after the ticking stopped and all of a sudden there's a complete loss of breaks they locked up and the driver was unable to efficiently stop while going down a hill Road. Driver had to use the emergency brake to make the other brakes release and then the brakes from there would not work even though you could stomp on them stand on top of them there was no breaking power anymore. Vehicle was brought into a GMC dealership on the following Monday where they confirmed the issue was a failed vacuum pump connected to the engine and camshaft which is a known safety issue to GMC as part of an ongoing open case they had specialty coverage and bulletins regarding the Tahoe and Sierra but neglected to include the terrain on this issue. Cold the GMC manufacturer in both [XXX] and [XXX] to try and get cost assistance and specialty coverage as the vehicle as well under the mileage requirements but have been giving the push around and zero assistance. The risk to the drivers and passengers lives was significant as we were on the highway for1.5 hrand thankfully the brake lost didn't happen in full during that time. The repairs were completed and paid for in full by the client which should have been covered by the dealership and we are looking for cost recuperation and are now being ignored. Receipts are here to substantiate the claim. The ABS light is no longer on there was no warnings on the vehicle showing any issues or any codes as OnStar was called and diagnostics were received and the diagnostics came back clear prior to this happening, and following the break failure. Lack of codes and warnings is life-threatening and serious. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

NHTSA complaint #11751119 — an unverified report by a vehicle owner.

ENGINE

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.

NHTSA complaint #11737294 — an unverified report by a vehicle owner.

ENGINE

Brakes were hard to engage or press when stopping due to Vacuum pump stop working. Had to replace the vacuum pump

NHTSA complaint #11719833 — an unverified report by a vehicle owner.

ENGINE

Vacuum pump failure resulting in crankshaft sensor to completely sheer off.

NHTSA complaint #11708515 — an unverified report by a vehicle owner.

ENGINE

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. Very frustrated, I put 12,000 out of my college fund to have a reliable vehicle for my two kids and now this is all I have. A car that doesn’t run. I called warranty and the man I talked to even said that they get a lot of calls for these cars needing to be fixed. I am at a loss on what to do now. The below information about the incident is for the most recent one happening in September. I know that this sounds like a warranty and dealership issue but I guaranty if you send something out to terrain owners they will report major issues that they have had. Leaving them stuck in loans and no where to go.

NHTSA complaint #11691195 — an unverified report by a vehicle owner.

ENGINE

Broken piston land and ring. car went into 'limp mode' while driving on interstate. Taken to dealer, told new engine was needed.

NHTSA complaint #11672277 — an unverified report by a vehicle owner.

ENGINE

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. I brought it to my local mechanic, who took a look and said that it's a vacuum pump failure, and the result is a lot of metal shards were released into the engine when the vacuum pump failed. My mechanic recommended I take to a GMC dealer for further evaluation. I looked up the recall on this issue, and see that it impacts a lot cars, including the 2017 GMC terrain, but not my 2018 GMC terrain. I am going to take it to the GMC dealer but I'm afraid I won't be able to afford the repair, and it doesn't seem like there was anything I could have done to prevent this from happening.

NHTSA complaint #11667521 — an unverified report by a vehicle owner.

ENGINE

Timing chain. It had no warning and failed due to poor design and gm in Europe fixed/addressed the issue by installing a plate behind the tensioner a part that isn’t available in the us.

NHTSA complaint #11659131 — an unverified report by a vehicle owner.

ENGINE

My vehicle’s engine was the component that failed. I was driving home from work. It is a forty-two minute commute. I was five minutes away from home when the vehicle slowed down in speed to a cruise. There were no issues prior after startup. There were no strange sounds, no start up issues, and no lights on the dashboard at all. I noticed that the vehicle had put itself into neutral gear. When I tried to stop the vehicle by hitting the break, the break did not work. I put my foot on the gas pedal and the car did not speed up. I could not change the gears. There was nothing I could do. The vehicle came to a complete stop when it powered off. When the car was put into accessory mode, there was an error message that stated the engine/vehicle was in low power mode. I was not able to start the car’s engine again. It was useless. The only way to move the car anywhere was to have it towed. This failure was scary and dangerous because it occurred in the middle of the night on a main road. Cars are known to drive above the speed limit past midnight in this area. I was glad that there were no cars on the road at the time. I was not aware of this failure occurring for my vehicle no were there any other known recalls. After doing some personal research, I found that GMC and certain Chevy models are having this problem, but no source listed any GMC Terrains as affected vehicles; although the same thing that happened to other people happened to me. I purchased an extended warranty through Fidelity Warranty Services, Inc. (Platinum) when I purchased the vehicle. They were the ones that had done all the necessary inspections for the filed claim once the vehicle was taken to a GMC Service center: Anderson Buick in Cockeysville, MD.

NHTSA complaint #11655132 — an unverified report by a vehicle owner.

ENGINE

My check engine light comes on intermittently, since March 2024, after having Cabin & Engine air filters replaced. Each time, I’m told it is code P0171. This has happened too many times for my comfort. Usually, it happens around the time my gas gets below 1/2 tank or after I fill up my gas tank. Originally, I was told by the mechanic that it could be one of four things, of which I’ve now had some of things done. InIn Aug. 2024, the check engine light came in. Code was P0171. Mechanic replaced the Brake vacuum pump. Once incident, almost a month later, on 9/24/24, was very scary. While driving on the interstate, I got ready to increase my speed, but heard a pop sound and noticed the speed wouldn’t accelerate. Next, the check engine light came on and the message in the dash popped up saying “engine power reduced” or something similar. I was able to coast from the fast lane over to the slower lane and off the highway into a parking lot. I turned the truck off. When I crunk it back up an hour later, it was shaking and jerking. While slowly driving, on the way to the mechanic shop, it jerked and shook each time I tried to accelerate after stopping at a light or slowing down with traffic. The code again was P0171. According to the mechanic, the intake hose had popped off. On 11/13/24, the check engine light came on. I again took it to have the code scanned and truck looked at. Test results again showed P0171. This time the Mass Air Flow Sensor was suggested. In a year I’ve had the fuel system cleaned twice, brake system flushed, & other routine maintenance such as oil change & brakes. Yet, my check engine light seems to still come on intermittently atleast once monthly. It came on two days ago, 2/18/25, when my gas was around 1/4 tank full. I added a fuel system injector, per mechanic suggestion, and filled my tank up with gas on today, 2/20/25. The check engine light had gone off within about 15 mins of me driving. I’m certain it will be back on soon with the same code.

NHTSA complaint #11644047 — an unverified report by a vehicle owner.

ENGINE

Brake vacuum pump failed causing engine damage. Camshaft on national back order. Vehicle has been in repair shop for 1.5 months waiting on part. No ETA. There has been recall for similar vehicles with same issue, failure, damage. But not for this VIN. It’s the same failure with same damage. How is this not a recall for this VIN?

NHTSA complaint #11643291 — an unverified report by a vehicle owner.

ENGINE

I got my car out of the shop a week ago for my brakes the car was in the shop for a month and this past weekend my car is doing the same exact thing a week later I was on I 75 also hit a semi truck

NHTSA complaint #11633068 — an unverified report by a vehicle owner.

ENGINE

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.

NHTSA complaint #11633081 — an unverified report by a vehicle owner.

ENGINE AND ENGINE COOLING

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.

NHTSA complaint #11631046 — an unverified report by a vehicle owner.

ENGINE

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.

NHTSA complaint #11618985 — an unverified report by a vehicle owner.

ENGINE

While driving the vehicle the vacuum pump failed and caused the camshaft to seize and physically break which caused the break peddle to become hard and breaking the vehicle was limited and almost nonexistent, which caused an extremely dangerous situation on the highway.

NHTSA complaint #11618092 — an unverified report by a vehicle owner.

ENGINE

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.

NHTSA complaint #11617538 — an unverified report by a vehicle owner.

ENGINE

In 2022 and now in sept of 2024 my entire braking system has failed. Cause you a complete in abilty to stop the vehicle. Upon this failure without any warning peice of the braking system connected to the engine shoots shrapnel into my engine and causes the cam to be destroyed. Now I can't get my car back because of a shortage on this part.

NHTSA complaint #11616710 — an unverified report by a vehicle owner.

ENGINE

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.

NHTSA complaint #11605416 — an unverified report by a vehicle owner.

ENGINE

The vacuum pump gears for the brake assist was shattered and metal parts were sent into the engine. I lost power brakes and was lucky to be able to stop the suv. The car was towed to a GMC dealer where it was diagnosed with a damaged exhaust cam, a shattered vacuum pump and metal pieces in the motor. Cost to fix $3200. This is a 2018 GMC Terrain with 112000 miles on it. I had a powertrane plus warrenty that was still valid but they refused to pay for anything. They claimed the vacuum pump caused the problem and it was not the engines fault. There were no warning check engine lights before this happened.

NHTSA complaint #11604413 — an unverified report by a vehicle owner.

ENGINE

The car very suddenly went into a reduced engine power mode, with check engine light and was immediately parked. Figuring I could turn the car off and turn it back on, however it sputtered turning off and shook violently before I was able to turn it off. It would then not turn back over, so I left it off and had a tow truck drive it to a GMC mechanic. The GMC mechanic was unable to diagnose an issue after days. I then had it towed to another local mechanic who stated the parts were "junk" and the engine needed to be replaced. Engine codes were related to the camshaft sensor and brake booster. It is my understanding the vacuum pump broke off into pieces, went into and destroyed my engine.

NHTSA complaint #11594454 — an unverified report by a vehicle owner.

ENGINE

While driving on the interstate the brakes all the sudden stopped working. I was able to stop the vehicle by pulling over to the shoulder of the road. I received a warning saying service brake assist and a check engine light after the brakes went out. The vehicle later shut off and is no start with no warning codes. I am currently towing the vehicle to a mechanic. Several people claim to have the same issue online stating that it is an issue with the brake vacuum booster shearing off in the exhaust cam which then causes major damage to the engine. It appears the same issue exists with several other GMC models that were already recalled

NHTSA complaint #11581218 — an unverified report by a vehicle owner.

ENGINE

While driving the vehicle which only has 68,000 miles the reduced engine power warning light appeared. As quickly as was safe the car was pulled to the shoulder. It was towed to the dealer who states the Vacuum pump seized causing the camshaft phase actuator locating pin to spin. Originally they stated a new camshaft and vacuum pump were needed at $3,500, but now state the entire engine is damaged and must be replaced at cost of $12,000. The vehicle was well serviced and this manufacturing flaw lead to the vehicle be stopped on the road putting both the occupants and others around at risk.

NHTSA complaint #11580131 — an unverified report by a vehicle owner.

ENGINE

Rear side windows in hatch area leaked filled up spare tire compartment with about 3-4 gallons of water. Now navigation doesn't want to work, sunroof not working, electric systems are not working right

NHTSA complaint #11573881 — an unverified report by a vehicle owner.

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. There must be a software code to easily allow this that the dealer can perform or a slight hardware modification to allow the operator to defeat AutoStop when it creates a safety hazard.

NHTSA complaint #11559359 — an unverified report by a vehicle owner.

ENGINE

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 PRİZE 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. There is a recall I noticed online for 2019 models and almost from the same area of throttle body, but nothing for 2018. Now, my wife and I hesitating to drive the car. Are we going to get stuck on the road again?

NHTSA complaint #11559269 — an unverified report by a vehicle owner.

ENGINE

There is an has been an issue with my electrical system says I purchased this car in 2017. Myself believe that the issues have not been documented until 2020. When my racy begins to run out, my engine light has been coming on and I’ve been getting the same code P1101 I took my vehicle to GMC and they told me that the engine light came on because the tape came loose. I brought this vehicle and there’s no way there should be no tape on it. The service tech also told me that if the problem continue to bring it back and I will have to pay $120 or whatever the label rate was for them to research I contacted GMC to file a complaint and I received the whole bunch of calls from a guy named Kevin. I believe he told me that he had been contacting [XXX] and no one returned his call and that he was sorry he couldn’t help me. This is my report number one of them from GMC. [XXX]. Everywhere I take my car they tell me that they have a lot of customers with the same issue and they tried to replace what the code is matching which is the mass airflow sensor but that does not help there is some type of problem with the engine or the electrical system with this vehicle. I am not the only consumer that has had this problem. I don’t know what to do. I have two kids I cannot afford to keep pay and label rate for them not to find the problem. I am also attaching the typical email that GMC sent out when they are working with the dealerships because I have been in contact with them and the person that was calling and then they sent me this email. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

NHTSA complaint #11558439 — an unverified report by a vehicle owner.

ENGINE

Last year this time brakes went out at 50 mph power brake module imploded from inside out. The part was on national back order. Second incident car stopped immediately while traveling 40 mph no warnings or anything both incidents could of been horrible . Not sure on second incident the issue yet car is in shop. Both incidents are safety concerns for myself and others. Driving at average speeds and something malfunctioning is a great concern of mine. I contacted GMC no one to talk too just chat and the person on the other side told me it was no concern of theirs all was dumbfounded by the conversation but until I said I was putting on social media and bringing to everyone attention her entire tune changed in regards to part and service. So I researched locally and luckily I found the part they had one left and I was told by dealer that it is an issue on these vehicles. Both safety incidents have been within a year of each other 2022 and 2023

NHTSA complaint #11534972 — an unverified report by a vehicle owner.

ENGINE

The vacuum pump started leaking and the car was parked immediately. When The pump was pulled out to be replaced, the reason for the leak was identified. The vacuum pump had busted into small pieces which are now in the engine.

NHTSA complaint #11533352 — an unverified report by a vehicle owner.