2018 GMC Terrain: sudden loss of power

Filed Oct 14, 2026 · Brakes, Engine · IN

On XXX while driving my 2018 GMC Terrain SLE 1.5L turbo on the highway at approximately 70 MPH near [XXX]. I experienced a sudden loss of power brake assist without any prior dashboard warning lights or messages. I was traveling with children to [XXX] for a youth wrestling tournament, approximately 5 hours from my residence. The brake pedal became extremely hard to press, requiring excessive force to slow the vehicle while traveling at highway speeds. I was transporting children at the time, creating a serious safety concern. Because I was away from home and needed to get the children to their scheduled wrestling weigh-ins, I arranged alternative transportation through Enterprise. I was unable to have my vehicle inspected by a GMC dealership until XXX, after returning home. At approximately 93,614 miles, Ed Martin Buick GMC diagnosed an internally failed, engine-driven brake vacuum pump. The service advisor confirmed in writing that the pump had come apart internally and explained that a seized pump can strip the exhaust camshaft gear. The dealership documented missing metal material from the vacuum pump and camshaft gear, raising concerns about metal debris entering the engine. Diagnostic trouble codes included P0014, P0017, and P0556. The dealership estimated repairs at $5,960.79 but advised that the proposed repairs might not remove all internal metal debris. The service advisor stated that replacing the engine would be the only way to guarantee complete debris removal. GM has published technical service information, including PIP5835 and Bulletin 21-NA-268, addressing similar vacuum pump failures and associated damage. The vehicle remains unrepaired. I am reporting this incident because an unexpected loss of power brake assist at highway speeds, without advance warning, creates a significant collision risk for drivers, passengers, and other motorists. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Filed Aug 24, 2026 · Brakes, Engine · AL

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.

Filed Aug 10, 2026 · Brakes, Engine · MI

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.

Filed Jan 29, 2026 · Fuel system · 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.

Filed Dec 2, 2024 · Brakes · IL

The vacuum pump exploded and I lost power braking ability while going approx. 40mph. If I hadn't pressed down hard on the brakes to slow down, in less than 2 minutes I would have ended up in Lake Michigan, as I was heading east toward the on ramp for [XXX]. The problem has been confirmed by European US Auto here in Chicago, and I have photos. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Filed Jul 25, 2024 · Brakes, Engine · PA

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.

Filed Jun 14, 2024 · Engine · CT

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.

Filed Mar 29, 2024 · Engine, Transmission · CA

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.

Filed Jan 18, 2024 · Brakes · TN

My vehicle keeps showing “service brake assist” and “service TSC” lights. I was on a hill and the auto-start was engaged, as well as hill assist. When I let off the brake pedal slightly to get the car to come out of auto-start, the car acted like it completely shut off (radio went black and lost power) and the car just started rolling backwards quickly. If there was a vehicle behind me it would’ve %100 caused an accident. My wife and child ride in this car every day and this is the second time I’ve had serious issues with this car. The first time I was driving down the interstate and the brake vaccuum pump went out and I lost all brakes, I had to put all 180lbs of my weight on the brake pedal to get it to stop.

Filed Dec 3, 2023 · Brakes · GA

While driving down the road at approximately 55 mph, came up to an intersection, 4 Lane I was in the right lane to go straight, there was a right turn lane next to me. I applied the brakes, pedal was really stiff and very slow to respond, I was able to edge over into the turn lane cutting people off and just barely missing the vehicles in front of me. It took 5 car lengths to stop my vehicle. When I finally was able to get the vehicle fully stopped I was almost in the paths of the crossing traffic.. when the light turned green I was able to slowly cross the intersection looking for a safe place to pull over. Immediately crossing the intersection the Service Brake Assist notification appeared, about another half mile the vehicle informed me of loss of power and that it was reducing engine power (limp mode). I was able to find a gas station parking lot to put it. When I opened the hood I noticed quite a bit of engine oil located under where the brake assist pump was located. I had lost about 1.5 quarts of oil. I refilled that. The next day I returned with a tow dolly. The vehicle was started just long enough to load and unload it at home. We pulled the vacuum pump where upon inspection it was noticed that the part has exploded and so far we are still missing some pieces that may be inside the engine. This is a known and documented problem of this part and should have a safety recall issued. . I still owe over twenty eight thousand on this vehicle and it has only 109,000 miles on it. I hope we can find all the pieces and that the engine wasn't fately harmed. GMC needs to make this right, a lot of people could have been harmed.

Filed Oct 20, 2022 · Engine · FL

Camshaft failed during driving causing vehicle to become disabled in the roadway and almost hit many times. The camshaft is being repaired by ase certified mechanic at an independent service center. A reduced power notice cam on a few minutes prior to the failure.

Filed Nov 25, 2018 · Driver assistance, Engine · 752 miles · AL

Driving on a downslope heading north on 65 going into tennessee from alabama I experienced a loss of power system lights went off along with gauges going off and on. At which time stabiatrak and transmission lights came on saying to pull over immediately.we did so called gm onstar where they told us we would experience a loss in power but could travel onward. We chose to get towed, however due to the holiday we had difficulties getting a tow and were forced to drive home 90 miles away. The problem did not present itself again on the drive home. We took it to a gmc dealer in vestavia hills they pulled off the codes but had no reason for the issue nor were they able to get service bulletins from gm on the issue. I documented the findings went home and a later on 11/23/18 the problem occurred at about 130 miles from the first incident. This time it happened going up a hill and giving the car gas did nothing to get me up the very small grade. I had to put it in reverse and get a running start at the hill in order to make it home. I called gm again and requested a tow to a second dealer in trussville, al they were unable to even see it until monday 11/26/18. I am very fearful that if we have to drive it again that I may not be as lucky.