2018 GMC Terrain Owner Complaints

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 ID

11755920

Incident

Jul 29, 2026

The contact owns a 2018 GMC Terrain. The contact stated that while driving at an undisclosed speed, the brake pedal was depressed; however, the vehicle failed to stop as intended. The contact stated that the brake pedal was abnormally firm. The brake pedal was depressed to the floor, and the vehicle came to a stop. The check engine warning light was illuminated. The vehicle was towed to the dealer. The vehicle was not diagnosed. The contact referenced an unknown recall; however, the VIN was not associated with a recall related to the failure. The manufacturer was not made aware of the failure. The failure mileage was approximately 95,300.

NHTSA ID

11754433

Incident

Aug 2, 2026

Mileage

95,300 mi

Vehicle would slowly roll even when break is applied. It was confirmed by the service center that the break booster vacuum pump was only reading 8 when it should be at 27. It was not making enough pressure. The vehicle would not stop when break was applied.

NHTSA ID

11752244

Incident

Jul 22, 2026

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 ID

11751119

Incident

Jul 11, 2026

Vacuum pump that supplies vacuum to brake booster failed without any warnings beforehand leaving us without the ability to stop. Luckily was able to avoid an accident.

NHTSA ID

11742410

Incident

Jun 3, 2026

While traveling on the highway in traffic, brakes became very stiff when depressed after attempting to slow down to exit. Was able to put full bodyweight into the brake pedal to slow enough to exit and navigate to the gas station right off the exit. Had to roll stop signs and unsafely navigate traffic because brakes were not working. Service Brake System warning light came on after the incident.

NHTSA ID

11739875

Incident

May 24, 2026

Gas leaking from the hood. High pressure fuel pump

NHTSA ID

11739681

Incident

May 22, 2026

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 ID

11737294

Incident

Mar 15, 2026

Mileage

260,000 mi

We just got off the bus thruway and my brakes pedal got hard to press and it was hard to stop car I had to push on brake dry hard to get the car to stop it was jarring and o had to get my some and o to a safe place. Garage said it’s brake assist and he researched there’s is an active law suit against GM bc lots of Moses and models have this issue although they claim to know nothing about it

NHTSA ID

11726554

Incident

Mar 18, 2026

My car was t-boned on the driver side and no airbags deployed. The outer door and window exploded with the force. We were also hit from behind

NHTSA ID

11724819

Incident

Mar 13, 2026

The control knob that controls AWD, 2WD,Off-road, and 4 x4 AWD. Just stopped working. Stuck on 2WD mode. I did have it checked for any codes, even though, there is NO check engine light is on.

NHTSA ID

11722587

Incident

Mar 6, 2026

The contact owns a 2018 GMC Terrain. While attempting to shift to reverse(R) out of a parking spot, the message “Transmission Unable to Shift” was displayed on the instrument panel, and the transmission was unable to shift into reverse(R). The contact called for tow truck assistance. The vehicle was unable to shift into neutral (N). The contact stated that prior to the transmission failure, the “Service Transmission Soon” message was displayed. The vehicle was towed to a local dealer to be diagnosed, and it was determined that the transmission had failed and needed to be replaced. The vehicle was not repaired. The manufacturer was not informed of the failure. The failure mileage was approximately 245,000.

NHTSA ID

11721631

Incident

Feb 27, 2026

Mileage

245,000 mi

Faulty Brake Vacuum Pump!!!! 2018 GMC Terrain @ 119254 miles--- NO warning! Brakes were hard to press, did not work and I rolled into ditch to prevent an accident. I see hundreds of people with same issue now that I Am having to research. This was very scary. I was told it was as a brake booster pressure sensor. But that was not the problem. It is the brake vacuum pump. This is so dangerous. Why is GMC not correcting this issue? This is insane. GM issued multiple technical service bulletins on vacuum and booster issues starting in 2017. Why hasn't anything been done?

NHTSA ID

11721477

Incident

Feb 27, 2026

Vehicle will not shift out of park, despite replacing the valve body, putting in a new battery, and transmission fluid. It has been this way since mid January. The codes don’t make sense and there is no current recall, nor have we had this vehicle for very long. It has 48,000 miles on it and is having this issue. Very disappointed.

NHTSA ID

11720574

Incident

Jan 24, 2026

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

NHTSA ID

11719833

Incident

Feb 19, 2026

The contact owns a 2018 GMC Terrain. The contact stated that while driving at various speeds, there was an abnormal grinding sound coming from the vehicle while transitioning to 4WD. The contact continued driving and the driving sound became more frequent while shifting into 4WD. Upon inspecting the vehicle, the contact discovered that the driveshaft had detached and was hanging down from the suspension. An independent mechanic was contacted, and the contact was informed about NHTSA Campaign Number: 17V516000 (Power Train); which the mechanic associated to the failure. The contact called two local dealers and was informed that the VIN was not included in the recall. The manufacturer was notified of the failure, and the contact was referred to the NHTSA Hotline to report the failure. The vehicle was not repaired. The failure mileage was approximately 160,000.

NHTSA ID

11716669

Incident

Jul 1, 2025

Mileage

160,000 mi

Turbo boost went out in my vehicle and 3 others with the same engine, different makes/models. Vehicles were serviced at Grayling Car Care 4430 M-72, Grayling, MI 49738 (989) 348-3200. Significant power loss, sluggish acceleration, poor fuel economy, and often strange noises (whining, grinding), accompanied by blue smoke from burning oil and a lit check engine light, with the severe risk of catastrophic engine damage from broken parts entering the engine if driven, requiring prompt replacement. It's generally unsafe to drive with a bad turbo, as metal fragments can destroy the engine.

NHTSA ID

11714113

Incident

Jan 19, 2026

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

NHTSA ID

11708515

Incident

Jan 2, 2026

The infotainment system will just randomly start going haywire and when it happens, you cannot use the touchscreen. It will try to randomly delete app icons such as the camera, it will try to delete connected phones, it will try to delete radio favorites and it will move app icons all around. These are just a few examples of things that happen.

NHTSA ID

11704389

Incident

Nov 1, 2025

The contact owns a 2018 GMC Terrain. The contact stated that while driving approximately 30 MPH, the brake pedal became extremely difficult to depress, with the message "Brake Assist" displayed. The vehicle was driven to the shoulder of the roadway and the parking brake was activated, and the vehicle was turned off. The contact stated that the transmission failed to shift into gear, and the vehicle was dragged onto a flatbed truck and towed to the residence. The cause of the failure was not yet determined. The local dealer and manufacturer were notified of the failure, but no assistance was offered. The failure mileage was 132,386.

NHTSA ID

11703650

Incident

Dec 7, 2025

Mileage

132,386 mi

The contact owns a 2018 GMC Terrain. The contact stated that while driving at an undisclosed speed, the vehicle shuddered and failed to come to a stop while the brake pedal was depressed. The check engine warning light was illuminated. The vehicle was taken to a local independent mechanic, where it was diagnosed with a locked brake vacuum pump. The contact was informed that parts of the brake vacuum pump had entered inside the camshaft and valve cover. Several unknown local dealers were contacted. The vehicle was not diagnosed or repaired because there was no recall associated with the VIN. The manufacturer was made aware of the failure. The failure mileage was approximately 183,000.

NHTSA ID

11700844

Incident

Nov 12, 2025

Mileage

183,000 mi

The contact owns a 2018 GMC Terrain. The contact stated that the transmission was shifting gear erratically. The contact stated that the doors were locking and unlocking independently, and the instrument cluster was blank. There was an abnormal beeping sound coming from the vehicle. Additionally, the contact stated that while at a traffic light, the Auto START/STOP feature delayed to respond. OnStar was alerted, but the contact declined to perform the service. The contact was in contact with the independent mechanic who sold the vehicle, but no assistance was provided. The local dealer was contacted. The vehicle was not diagnosed or repaired. The manufacturer was contacted, but no assistance was provided. The failure mileage was approximately 130,000. The VIN was not available.

NHTSA ID

11698239

Incident

Mar 1, 2025

Mileage

130,000 mi

My car said to me this not that there is something wrong with the Service Safety Restraint system! It was fine last night when I got home! I just bought this car a month ago and everything was fine and now my air bag light is on and will not go off!

NHTSA ID

11696252

Incident

Oct 29, 2025

The contact owns a 2018 GMC Terrain. The contact stated while driving at an undisclosed speed, the air bag and ABS warning lights illuminated. The vehicle was taken to Auto Zone to be diagnosed. The vehicle was diagnosed with air bag failure. The contact was informed that the air bag needed to be replaced. The vehicle was not repaired. The dealer was made aware of the failure; however, the contact was informed that there were no open recalls on the VIN. In addition, the contact was informed that once a recall repair was completed, it would not be performed a second time free of charge. The manufacturer was not made aware of the failure. The failure mileage was approximately 95,100.

NHTSA ID

11694159

Incident

Oct 3, 2025

Mileage

95,100 mi

The contact owns a 2018 GMC Terrain. The contact stated that while driving at an undisclosed speed, the unintendedly decelerated and failed to properly accelerate. The vehicle was taken to the local dealer, who diagnosed the vehicle with transmission failure. The contact was informed that the transmission needed to be replaced. The transmission was replaced with a used transmission, but the failure reoccurred. The vehicle was taken back to the local dealer who diagnosed and determined that the replacement transmission had failed and needed to be replaced. The vehicle was not yet repaired. The manufacturer was not notified of the failure. The failure mileage was 53,000. The VIN was not available.

NHTSA ID

11692086

Incident

Jul 25, 2025

Mileage

53,000 mi