Equipment Problems of GMC Terrain - part 1

GMC adaptive learning transmission problems that lead to safety concerns, emissions reduction in mpg, and increased wear of the transmission. Regarding gm’s 9t45 automatic 9 speed transmission. Problem: - the gm adaptive learning of the transmission does not have safe guards in place to prevent unsafe sift patterns and behavior. This results in shift flair behavior where the transmission will drop out of 3rd gear and pause before shifting to 4th gear. It will learn to lock out 9th gear and it will max out with 8th gear at freeway speeds reducing mpg. And it will fail to downshift appropriately while driving leading to the operator wondering why the vehicle will not accelerate when needed; this casual downshift delay then results in excessive downshifting to the lowest possible gear where the vehicle will then lurch forwards; and then it will pause and maintain said lower gear and continue accelerating for 1-2 seconds while the operator presses the brake pedal in response of the vehicle jumping forwards. Individual situations: 1) lack of 9th gear use at freeway speeds. This is reducing the advertised emissions based on epa testing. This behavior skews official epa test results because vehicle operation is not as advertised. 2) shift flair and unsafe shift delays. This is the most serious behavior. It leads to pauses and delays in acceleration of up to 5 seconds, and it leads to pauses and delays where the vehicle continues to accelerate up to 3 seconds after letting off the accelerator and pressing the brake. 3) excessive wear. The badly learned behavior is causing issues with shift control pressure and logic, excessive clutch wear leading to damage and worn clutch packs. Analysis: - resetting the gm transmission adaptive learning to factory removes these problems, the trans will relearn bad behavior within 2-3 weeks of daily driving. Reset was performed using an autel hot function “quick learn” procedure for the transmission.

See all problems of the 2024 GMC Terrain 🔎.

Without any type of warning, I was driving down the road when my car started making a knocking/ticking type noise then my engine light came on. I attempted to hit my brakes and stop, and I had no control. There was no brakes without pushing it all the way to the floor it was very hard to get my car to stop. I managed to get off the road and into a parking lot and now told that I have $5000 worth of repairs, including the vacuum pump, camshaft timing and guides. After reading information I see there is complaints filed regarding this failed vacuum pump and I would just like to report this.

See all problems of the 2018 GMC Terrain 🔎.

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.

The car just stopped accelerating and the check engine light came on. I took it to a shop and they had to replace the fuel pump control module. There is already recall for some 2022 GMC Terrains but my vehicle is not included in the recall. I dont understand how a 2022 GMC Terrain has a recall for the fuel pump module but my 2022 GMC Terrain is not part of the recall already put out and I have the same exact issue as the other vehicles that had been recalled.

See all problems of the 2022 GMC Terrain 🔎.

I recently pulled over to help a woman driving a 2026 GMC Terrain who had run out of gas in the middle of xxx in virginia. Obviously, the first priority was to get the vehicle out of the travel lanes and onto the shoulder. I tried to figure out how to put the Terrain into neutral so we could move it, only to discover that * vehicle cannot be shifted into neutral if it is not running. ** since it was out of gas, it could not start, meaning we could not put it in neutral and could not move it out of the roadway. Fortunately, a vdot safety service patrol truck came by. The driver stopped to help and thankfully had gasoline. However, I was told that, according to policy, he could not put gas in the vehicle while it was still in the travel lanes. This created an extremely dangerous catch-* vehicle could not be moved because it could not start, it could not start because it was out of gas, and gas could not be added because it had not been moved out of the roadway. ** I believe this is a serious safety issue with the vehicle. A disabled vehicle should have a reliable way to be placed in neutral regardless of whether the engine can start. This is especially important after a breakdown or crash, when the vehicle may need to be moved quickly to protect the occupants, other drivers, or first responders. If there is a manual emergency procedure for putting a completely disabled Terrain into neutral, it should be clearly documented and readily accessible to drivers and roadside assistance personnel. If there is no practical method, I believe GMC needs to address this design. A modern vehicle should not become an immovable roadblock simply because it ran out of fuel. Please investigate this issue and take whatever action is necessary to ensure disabled vehicles can be safely moved out of active traffic lanes.

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.

My car wouldn’t start in my driveway. . Onstar sent me an email with code p129f ( fuel pump driver control module) failed. I am thankful I wasn’t driving down the highway when it went out. My husband took it to lexington park Chevrolet Buick GMC dealership, where we bought the car and they replaced the part. My car only has 41,898 miles. My VIN #: [xxx] , a 2022 GMC Terrain denali. I noticed online that other 2022 GMC Terrain has a recall on this part, but not my VIN #. I feel my vehicle should also be part of this recall. Information redacted pursuant to the freedom of information act (foia), 5 u. S. C. 552(b)(6).

The car suffered a long crank, then stalled completely while moving on a public road, which is a severe safety hazard.

When the gas is mashed to accelerate, the car does not want to go. It has left me stranded and rolling in the middle of traffic. I am scared to drive it.

See all problems of the 2020 GMC Terrain 🔎.

During heavy rain, the sunroof on my Terrain leaked badly enough to allow a substantial amount of water into the vehicle. The rear floor area became completely saturated, and the sunroof controls stopped working. I brought the vehicle to hudson Cadillac Buick GMC in poughkeepsie, new york, to have the problem diagnosed and repaired. The resulting repairs and water-damage cleanup cost me nearly $3,000 out of pocket. I was advised that the damage was not covered by my warranty or by my insurance. What concerns me most, however, is that this does not appear to have been an isolated incident. While my Terrain was at the dealership, I learned that four other GMC Terrains were also at the dealership experiencing water damage related to leaking sunroofs. Mine was the fifth. Finding five Terrains at the same dealership with what appeared to be similar water-intrusion problems was extremely concerning to me and made me question whether this is a recurring issue with these vehicles. I also have a video provided by the dealership documenting the water damage to my vehicle, and I am happy to provide that video, my repair invoice, photographs, or any other documentation you would like to review. They went to great lengths to dry the vehicle, which was especially important to me because I was extremely concerned about hidden moisture and dangerous mold. Thankfully, after their work, there is no odor and no indication of remaining moisture or mold, and I am very satisfied with the quality of the repair and cleanup. The extent of the water damage was frightening. At one point, I was genuinely concerned that I might have to get rid of the vehicle simply because I was afraid of the long-term consequences of having so much water inside it. I am very grateful that the dealership was able to restore the vehicle so thoroughly but there is still a possibility that the repair will fail and I will have to replace the sunroof module.

The rear access closes on its own after sitting open for a period of time. I was sitting at grocery pick up with the access open. This caused it to close on worker at grocery pick up. It stayed closed and I had to hit the button to open it back it did not auto go back up when it couldn’t close.

The back passenger seat exploded and caught fire, burning the back of the seat in front and burning the ceilings. Inside the whole vehicle is black from smoke damage. Incident assessed by fire marshal who has ruled as electrical issue. No warning lights or systems displayed anything.

My vehicle is making a squeaky sound/noise when breaking and getting louder. I took it in for service and they couldn’t seem to find the issue. It’s coming from the front end of the vehicle.

The screen calls my own phone number and hangs up over and over if I just ended a call. I am not able to use any part of the screen afterwards such as my map. It stays like that until I disconnect the bluetooth and wifi from my phone while trying to drive. Safety issue!.

Backup camera stopped working and displays a blue screen stating “service backup camera. ” this was an issue when the vehicle was under 3 year manufacturer bumper to bumper warranty and was fixed by dealer at no cost. Now this same issue has occurred again approximately 3-4 years later. I thought at first this was an issue specific to my vehicle but now after doing research I see this is an issue across several GMC terrian vehicles and other gm vehicles. This issue should be fixed by the manufacturer for all vehicles affected. Vehicle owners should not be responsible to fix faulty parts from the manufacturer.

On June 7, 2026, I was driving my 2020 GMC Terrain. I was going at about 40mph along a very busy main road. While slowing for a red light the check engine light turned on and the car displayed a notice about reduced engine power. Seconds later, the brake pedal became stuck and would not press down all the way and I lost braking ability. The car rattled/shook violently, made a grinding noise, and then the engine shut off and the car stopped abruptly, narrowly avoiding hitting the car in front of us. I turned on the hazard lights. I was not able to get the car to start again, nor was I able to get the car to shift into any other gear including neutral. We were nearly hit by other vehicles multiple times while attempting to get the car to move again, and to get myself and my child safely out of the road. Myself and multiple bystanders attempted to engage the transmission interlock override multiple time. We were eventually able to engage it and push the car to the side of the road. This failure created an extremely unsafe situation for all involved as this road is very busy and there were numerous near-collisions both with my disabled vehicle, and with other drivers serving out of the way and into other lanes at the last second. As time went on and the battery drained, most of the car's exterior lights turned off and other drivers had a hard time seeing my car. I used a strobe flashlight to alert other drivers but this required that I had to stand in the road near the vehicle. Police were called immediately when I found that we could not move the car out of the road, but they did not arrive. Ultimately the vehicle was stuck and inoperable in a travel lane for over two hours. The car was then towed to a nearby repair shop. The mechanic evaluation stated that the brake vacuum pump had failed resulting in loss of braking ability and expensive damage to the engine and other components. The manufacturer is aware of this issue. See: thieme, et al. V. General motors llc.

Vehicle stalled while driving and would not restart. Strong gasoline smell present and on ground. Third occurrence. Vehicle stalled while driving at on busy road (safety issue both times). Strong raw gas smell. Would not crank afterward. Dash powered normally with check engine light. Happened previously around 27k miles in September 2025. Occurred again may 9, 2026. Occurred again today l, may 18, 2026. Vehicles is being towed to dealership again for the 3rd time.

See all problems of the 2023 GMC Terrain 🔎.

The sun/moon roof randomly imploded while driving. It popped and felt the force of the implosion.

I have had 2 different instances where my vehicle stops in the middle of a busy intersection or traffic and have no warning what so ever. Vehicle just shuts off and I am not able to turn back on to move out of the way. First time I got it repaired it was related to the fuel pump and now I am waiting to hear back from my mechanic to see what the issue is but so far it is an indication of the fuel pump as well. Both times I required help from law enforcement because vehicle shut off in the middle of the road and safety to myself and other drivers was an issue until tow truck arrived to move my vehicle.

Car reduced speed and the smell of gas filled the car. Car shut off. Check engine light came on with reduced speed. This is the second time this has happened. Gas leaked onto ground from car. Car stalls immediately while driving and does not allow you to press the gas to keep moving. Almost hit from behind on main street.

Filled up with gas and went to leave gas station and was still rolling to come to a stop and car shut off and would not crank back up o couldn't put in neutral to even move out of the way. After about 10 mins I was able to crank it back up. No lights came or was on and battery was showing 14. 5 now that im sitting battery is showing 12. 8. Oil was just changed 4 days ago. Just purchased used less then 3 weeks ago. Im at a lost has 122,272 miles on it.

I bought this car new from davidson's in rome, NY in early March 2026. This is a 2026 model. Two days after I took possession, I noticed that the spare tire well was halfway full of solid ice. The car has a severe leak through the back right side window. The dealer states it needs to be replaced. The interior frames of the car were loaded with water for many weeks as it stood on the lot. Had the dealer done a final inspection of this car prior to transferring ownership to me, as they should have and stated they did, they would have found the solid ice that surrounded the spare tire and investigated the leak and repaired it but they would have been required to tell me of this leak I assume. . . If so, I would never have bought this car. They had the car in the shop now for 3 weeks as of today, April 20th, 2026, and no word on the resolution. They did give me a loaner car for use. They have to dry the car out completely and dehumidify it as well as replace the window that leaked. The risks going forward is to the internal wiring, mechanicals, etc. Due to static water exposure for many weeks prior to the sale. Had the dealer done their job with prior inspection, this could have been avoided. I asked them for my money back and they refused so I am stuck with a brand-new car that was essentially flooded with rainwater because the dealer did not do a final inspection prior to my accepting ownership of it. I wrote letter to all the dealership principals involved and none of them answered me directly. . . As if I was invisible or completely silent on this issue. If given an option, I would give them this car back and get a full refund.

Onstar module not working.

See all problems of the 2025 GMC Terrain 🔎.

This just started on it's own. Back up rear camera shows distortion from time to time and appears to be getting worse or happening more.

Took dealer 3/26 for sam issue engine power reduced after already cause me hit curb. Got it out 4/1/26 now 4/5/26 it happened again same codes after they claimed they fixed it. Also keep having emergency services come on a caused my dashboard out. My issues is car keeps stalling losing power. Same codes as week ago after dealer fix. Also 4 time took for noises in my car from passenger side. They keep telling me they can’t replicate it, but you can clearly see where the door is not lined up. This has been going on for over 30,000 miles for that. Like some of these issues have been going on since the 36,000 but now I’m having issues where I’m losing power like this is insane all before 60,000 miles which I’m about to hit. It’s gonna end up getting me killed on the interstate. My VIN also says it’s fwd it’s awd at4 . Called dealer said only to update software clearly not the issue. My doors are off and they have refused to fix those for over 30,000 miles now. It won’t let me attach any pics for some reason I’ve tried since yesterday.

While driving the vehicle became extremely difficult to stop I was advised that the vacuum booster pump was broken and it needed to be replaced. This was first completed 09/24/25 by gateway tire and service center. I was advised that there was a service bulletin for the issue. Then I have had the same thing happen and I returned the vehicle to the same repair shop and I was advised that the vacuum booster pump was broken and it caused the exhaust camshaft to break, as well as the timing was out. The shop had to replace several things in order to repair and I was responsible for the cost. There was no warning before either of the incidents.

See all problems of the 2019 GMC Terrain 🔎.

Vacuum pump exploded into camshaft and engine area, causing me to lose brakes completely on the highway. Costly repairs to clear out metal shrapnel and replace camshaft.

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.

While driving several times smelt gas and car cut out engine came on and car stopped mid driving multiple times. Says they replaced fuel pump reset car etc.

The screen continues to go out. Screen contains many safety functions. When it malfunctions it is distracting.

Got everything under the hood done n still have the same problem with it shut off while driving.

See all problems of the 2010 GMC Terrain 🔎.

I had a message flash that said the power to the engine was reduce. Next message said check stabilink ( or something similar). . It said drive with caution. I live 2 mins from my job I drove home and pulled in the driveway I then felt the car act like it wanted to shake. This was on 2-10-26 I contacted onstar asked them to run a diagnostic. The codes that came back p0016 p0089 p228d are very well known codes with many people with the same vehicle/engine that have had to replace the engine. The engines have known issues had I known that maybe I could have replaced a part or two or three or four to have a stable vehicle now my vehicle is currently at GMC dealer since Tuesday morning actually had it towed there Monday night. I called Wednesday evening they still wasn't sure the "issue". Thursday I wait until about 1pm spoke with john he said well we are pretty sure you need a new engine the mechanic is checking a few more things the car has no pressure. About a hr later I get a email and a call saying the timing chain skipped and something about the pistons and the valves and I need a new engine . John called me and said well. Ill tell you what we will offer you a brand new engine for the same price as a rebuild plus you get 3yrs 300 thousand warranty for 10,944. Give or take a few dollars. We'll first I paid like 15,500 for the car that I just litetally paid off like Jan 12026. I really feel like had GMC made buyers aware that the vehicle has defective parts/engines buyers could replace parts or GMC should be held accountable. I started googling the engine and found out that there is a class action lawsuit and a recall on " certain" 2017 Terrains depending on the VIN. Same issues my car is having but its saying my car has no recall.

See all problems of the 2017 GMC Terrain 🔎.

The pcv valve froze which caused pressure to build up in the rear main seal to fail. Causing oil to leak out of the motor. Hence the motor won't hold oil.

Vehicle did not go into park when the ignition was turned off. Car started to roll while passenger was getting out of the vehicle as another vehicle was parking beside us. The other vehicle could not avoid our rolling vehicle. Passenger had to quickly sit down to avoid being hit. The next day the vehicle was taken to the dealership, and they could not find anything wrong. They gave us a copy of bulletin#08-07-30-026i. We were not aware of any problems or bulletins being issued prior to the accident. We had repairs of $2,705. 71 and don't know what the other driver incurred.

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.