2018 GMC Terrain

Approximately 3 miles from my residence my car display flashed "Reduced Engine Power" and slowed down. When I reached a stop sign and tried to stop, my brakes were stiff and I was unable to stop. I went through the stop sign. I continued to my residence at 10mph and backed into a parking space with a curb to help stop my vehicle. I turned the car off and called a mechanic to come look at my car. I explained the events and let him know it would not start. He checked the codes after hooking it up. The error codes were for Cam shaft and crank shaft, etc. I was instructed to not try and start the car because further damage could occur and it would need the camshaft pulled to determine the extent of damage.

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.

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)

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.

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.

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.