GMC Terrain loss of power problems

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 Oct 5, 2026 · Engine · 65,000 miles · FL

The contact owns a 2014 GMC Terrain. The contact stated that the exhaust manifold was previously replaced due to an exhaust leak and the vehicle was towed. The contact stated that the vehicle was experiencing excessive oil consumption, and a quart of oil was added every 500 to 1,000 miles, causing an abnormal engine ticking sound and timing chain sound. The check engine warning light was illuminated. The contact retrieved DTC: P0420. The vehicle was taken to an independent mechanic, where the timing chain and catalytic converter were replaced; however, the failure persisted. The contact stated that the engine ran rough and experienced reduced power, and the vehicle was idling rough and the vehicle hesitated while accelerating. The contact became aware of an abnormal oil odor during the failure. Additional trouble codes P0017 and P0420 were retrieved. The failure mileage was approximately 65,000.

Filed Oct 1, 2026 · Steering · FL

The Electric Power Steering (EPS) gear assembly / rack and pinion failed completely. Yes, the component is available for inspection upon request; it is currently located at the servicing dealership. A total failure of the steering gear assembly caused immediate loss of power steering assist, making the vehicle extremely heavy, rigid, and difficult to steer or control. This sudden mechanical/electronic failure puts the driver, passengers, and other motorists at extreme risk of a collision, especially if it occurs at highway speeds or while negotiating a turn. This did fail on me driving down the Highway! Yes. The problem was officially diagnosed and confirmed by the franchise dealership. They quoted $3,500 to replace the failed assembly. The vehicle displayed a "service power steering" warning message on the dashboard alongside an immediate loss of steering power assist. The failure happened suddenly while driving with no prior mechanical warning signs, symptoms, or gradual degradation.

Filed Sep 29, 2026 · Engine · MO

I have had my check engine light come on for P0299. I've lost power while on the road. Had my turbo replaced and now the same issue is starting again. I'm afraid of my car stalling out again with my child in the car. This is a definite safety issue especially since this is happening again months after getting the new turbo put in.

Filed Sep 13, 2026 · Electrical, Fuel system · NC

My 2022 GMC Terrain lost power and stalled while I was driving, creating a safety risk because I could no longer maintain speed in traffic. The incident involved a police response and a safety-related tow costing $250. On XXX, OnStar recorded diagnostic trouble code P129F. Tire Choice subsequently replaced the fuel pump control component, identified in my records as GM part number 13554821, at a repair cost of $493.25. I have supporting diagnostic, repair, towing, and police documentation, along with evidence of the removed part. GM’s later vehicle history printout showed zero open field actions for my VIN [XXX]. I am concerned that this failure may be related to the fuel pump power control module condition described in GM campaign N252516900, although I have not confirmed that connection. I request that the federal safety agency investigate the loss of propulsion and whether the campaign’s coverage should include my vehicle. Tire Choice subsequently replaced the fuel pump control component, identified in my records as GM part number 13554821, at a repair cost of $493.25. I have supporting diagnostic, repair, towing, and police documentation, along with evidence of the removed part. GM’s later vehicle history printout showed zero open field actions for my VIN. I am concerned that this failure may be related to the fuel pump power control module condition described in GM campaign N252516900, although I have not confirmed that connection. I request that the federal safety agency investigate the loss of propulsion and whether the campaign’s coverage should include my vehicle. 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 19, 2026 · Brakes, Engine · CT

While driving, I suddenly smelled something burning. Immediately after, a warning popped up stating 'Engine power is reducing,' the check engine light came on, and I experienced a sudden, near-total loss of power braking assist, making the brake pedal extremely hard to press. I had to use intense force to bring the vehicle to a stop. A scan of the vehicle's OBD-II codes revealed codes P0556 (Brake Booster Pressure Sensor Circuit), P0014 (Exhaust Camshaft Position Timing Over-Advanced), and P0017 (Crankshaft Position - Camshaft Position Correlation). This is a known failure where the engine-driven mechanical brake vacuum pump seizes up, destroys the braking vacuum assist, and bends or shifts the exhaust camshaft reluctor wheel, causing a severe and immediate safety hazard while in motion.

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 Aug 9, 2026 · Brakes, Engine · MI

While driving my 2019 GMC Terrain on local roads, the vehicle suffered a sudden and complete failure of the braking system. The brake pedal became extremely hard to press, and the dashboard displayed a critical error message stating 'Engine Power is Reduced.' during this frightening safety incident i felt lucky to bring the car to a stop without an accident. The vehicle had to be flatbed towed to a repair facility. This sudden loss of power braking is a known, documented defect matching the engine-driven brake vacuum pump failures currently subject to federal class-action litigation (Thieme v. General Motors). I am requesting a formal safety investigation into why the GMC Terrain was excluded from previous GM vacuum pump recalls despite posing an identical, life-threatening risk to occupants."

Filed Aug 5, 2026 · Driver assistance, Engine · MA

adaptive cruise disengaging alert on dash- no cars or weather conditions to induce this. loss of power and bucking on highway( near accident caused) catostostrophic sudden loss of power engine/transmission failure while mechanic driving resulting in car towed back to dealer. loss of power multiple times causing near accidents. sudden jolting at stop light causing car to propel forward requiered both feet on brake pedal to stop. 4 episodes of near collision 1st altert started 04/4/2024 adaptive cruise light on dash 14,700 miles on vehicle 5 episodes continued and now car is still at dealership for emissions failure, loss of power x 4 weeks. ALL PHOTOS OF DASH LIGHTS, REPAIR INVOICES AND VIDEO OF DASH AVAILABLE BUT I AM NOT ABLE TO UPLOAD ALL.