2020 GMC Terrain Powertrain & Transmission Problems

The intercooler has been a document problem on GMC Terrains for awhile now. I had my intercooler replaced and now less than 10 months it is having the same problem. The vehicle will go into reduced power mode which would be a safety hazard because it will also stall sometimes when it is having performance issues. That could lead to someone colliding into me if it suddenly stops when someone is behind me. I believe this part should be recalled and fixed for free.

The contact owns a 2020 GMC Terrain. The contact stated that while driving 35 MPH and depressing the accelerator pedal while driving uphill or making a left or right turn, the tires were skipping, and there was a clicking and whining sound coming from the front of the vehicle. There was no warning light illuminated. The contact stated that a friend test-drove the vehicle and informed that the vehicle had experienced transmission failure. Neither the independent mechanic nor the dealer was contacted. The vehicle was not taken to the dealer or an independent mechanic to be diagnosed or repaired. The contact related the failure to NHTSA Campaign Number: 20V668000 (POWER TRAIN); however, the VIN was not included in the recall. The manufacturer was notified of the failure and informed the contact that the VIN was not included in the recall. The failure mileage was 104,000.

I have been having intermittent problems for well over 1 year with my vehicle not accelerating. I try to accelerate from a stop, the vehicle does not respond. I have the accelerator pedal pressed to the floor nothing happens for 10-15 seconds, then vehicle will lurch forward and start responding. This has happened several times as I am pulling into traffic. Major safety concern that could cause severe injury or fatality. I also have other issues with vehicle not shifting gears, engine feels as though it is skipping while driving. I have taken this to the dealership and was told that they could not recreate the issue. No engine code or service lights have ever displayed. Dealership told me is can't be anything major since there are no codes or service lights. Currently have 72,000 miles, did purchase an extended warranty. I have seen many complaints of this same problem from other Terrain owners. GMC needs to fix this problem before someone is killed in a collision because their product won't accelerate.

I have been experiencing loss of power when going from a full stop to acceleration. I purchased my 2020 Terrain. I almost got in a car accident for the 3rd time today due to this loss of power issue. Stopped at a stop sign, I accelerate but the vehicle will barely move no matter how far down you push the peddle down. The loss of power is anywhere from 4 to 6 seconds then all of the sudden power will return. I've looked for recalls but there are none for my vin. This behavior is unpredictable and has occurred at stop signs, traffic lights, and when attempting to turn onto main roads. It has nearly caused accidents due to my inability to safely accelerate in time when merging or crossing traffic. I’ve read that GMC recalled certain 2021 and 2022 Terrain models for a fuel pump defect causing similar symptoms. My 2020 model is not currently included in that recall, yet it displays the same dangerous loss-of-power issue. I believe this is a serious safety defect that should be investigated and potentially included in the existing recall. I respectfully request that NHTSA investigate this issue further. I would also appreciate confirmation that this report has been logged. Vehicle Info: 2020 GMC Terrain VIN: [XXX] Engine: 1.5L Turbo Mileage: 62,142 Thank you for your time and your work in ensuring vehicle safety. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

The contact owns a 2020 GMC Terrain. The contact stated that while making a turn, the transmission shifted into neutral and briefly lost motive power and stalled. No warning lights were illuminated. The contact was able to restart the vehicle; however, the vehicle failed to function while shifting to drive(D) or reverse(R). The contact opened and closed the door to see if the vehicle would reboot. After several attempts, the vehicle returned to normal functionality. The contact stated that on a separate occasion, the transmission was leaking transmission fluid. The transmission was constantly slipping. The check engine warning light was intermittently illuminated. The vehicle was taken to the dealer, where it was diagnosed that the START/STOP accumulator in the cap was missing bolts, which caused the transmission to fail. An unknown code was provided to the contact. The vehicle was not repaired due to the cost. The vehicle was taken to various independent mechanics who confirmed that the transmission had failed. The manufacturer was made aware of the failure. The failure mileage was approximately 94,000.

On 6/22/2025, brakes stopped working while trying to make a turn. Next multiple engines light came and car went into reduced speed mode. As I tried to find a safe place to stop, the vehicle went into limp mode and shut down in the middle of the road. The dealership said the issue was the vacuum pump which caused the timing chains to break. There have multiple recalls for this exact issue but my car is not on the list. My manufacture warranty ended on 5/21/2025. When I spoke to a GM representative I was told there was nothing they can do because there is not a recall for my vehicle. They explained even though I had the same problem the recall is for other vehicles. GM also issued a warranty extention on the vacuum pump to 10 years 150,000 miles. However my vehicle is not on the list for the extention. this issue is a safety hazard regardless of the vehicle type. I was lucky that no one was behind me or they would have hit me.

[XXX] once again while diving down the road 45mph Terrain once again goes in to park ,I was lucky the lady behind me wasn't to close .Also I contacted onstar when I was able to get vehicle moving at the store ..I told her what happen she ran diagnostics while parked at store said there was no codes I let onstar know this has happened several times..I had no warning, no indication, no lights came on.And I also let her know that this same vehicle was still stalling I was at intersection and the auto/stop is always on it will not let you bypass or default took it to dealership who I bought CPO back when it first would not let me turn it off cause its stalls at stop signs ,red lights etc crazy thing is if you turn the ac on it cranks up , if you hit the door unlock it starts... Thats not normal GMC knows that the dealership whom sold me CPO that wasn't the misleading is beyond crazy..GSM cussed me out It comes with life time warranty but when I had it towed right after I bought it 2 months ..I was talking about what the mechanics had said that this vehicle was in prior flood and accident GMC onstar has a different Vin then the one that on the vehicle..The doors are not original I can see the inside of steering wheel and on dash where they said air bags were deployed and they did a [XXX] job hiding it ... I paid over 32k for this 2020 Terrain that was advertised as CPO with 1 owner in Florida they showed me a fraudulent carfax, I pulled up my own and it came from New York ..This vehicle is not safe to drive but I dont have any other options..I have made complaint with both GMC and my finance company whom also wrote complaint on dealership and the told me I could rewind the loan but when I told dealership I knew that they sold me a vehicle that was not CPO and what I learned He came at me at dealership infront of workers and customers .. The vehicle just going to end up getting myself killed or someone else.. Semi had to run off road to avoid hitting me INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

The engine in my 2020 GMC Terrain is consuming oil at an alarming rate, burning through a full supply within one hour of operation. This excessive oil consumption has repeatedly caused significant damage to the coils and spark plugs, rendering them ineffective within 24 hours. The issue has led to multiple cylinder misfires, poor vehicle performance, and a transmission stall, posing a serious safety risk while driving. The GMC mechanic at Jim Ellis Buick GMC diagnosed the problem as internal damage to the pistons, which they state requires a full engine replacement. They also confirmed an internal oil leak within the engine, which is contributing to bad emissions and further degrading vehicle performance. This defect not only compromises the reliability and safety of the vehicle but also raises significant environmental concerns due to the excessive oil burning and emissions. I am requesting a thorough investigation to address this issue and determine whether it is part of a broader manufacturing defect affecting similar vehicles.

Gear selector

The vehicle is a 2020 and should not already be having electrical issues. The vehicle repair is over 5k for needing a starter motor, water pump and drive belt. A starter should last up to 100k miles and water pump should last 10 years not 4. This vehicle is a lemon and should not have so many issues.

While driving I had to push the brake to the floor and a light came on saying reduced engine power. I pulled over right away and had my car towed to mechanic. The vacuum brake pump exposed and parts went into the engine. The mechanic got all the parts out but now engine has low compression and needs a new timing chain. This is over $3,000 so far. Gm recalled other vehicles with the exact same pump ? Why not the terrain.

The contact owns a 2020 GMC Terrain. The contact stated that while at a stop, there was an abnormal burning odor coming from the vehicle, with the service brake assist message displayed. The brake pedal became firm, and the contact used excessive force to stop the vehicle. The contact pulled into a gas station and restarted the vehicle while the check engine light was illuminated. Despite the failure, the contact was able to drive the vehicle to the residence. The contact inspected underneath the hood and discovered an oil leak as well as black soot that had covered the entire engine. The dealer was notified of the failure and provided the contact with a diagnostic fee for an inspection. Upon investigation, the contact discovered NHTSA Campaign Number: 20V668000 (Power Train) which was linked to the failure. The manufacturer was not notified of the failure. The vehicle was not repaired. The failure mileage was approximately 57,000.

After heavy rain the backseat of the car was flooded as well as the rear wheel well likely due to the sunroof not draining properly. This led to electrical failure of the sunroof mechanism and potential to damage other electrical elements. This will be looked at by the dealership but have read that this is a known issue.

2020 GMC Terrain Engine stopped working. Put in new engine. After one week new engine blown. We were 2000 miles away on vacation. I need a free rental I was with no car for a month and after only one week again for 3 weeks. Compensation request: Lost wages Hospital visit Extra hotel nights Gas Food car and insurance payment

GMC 2029 Terrain Our car broke down three times after a new engine was put in. After one week it had to be towed again to put in a third new engine. It has been fixed since Aug. 1st but GMC has yet to reunite us with the car 2000 miles away. We’ve made car and insurance payments for almost three months with no vehicle in our possession. It was under warranty. No loaner or rental car has been issued to us. Nobody calls us back. Terrible customer service by GMC.

2020 GMC Terrain SLE Elevation Package 83,000 miles and needs complete engine rebuild @ cost of $10,700 per Dealership Service. Was told “I drove the vehicle with low oil” which Inturn is the cause of needing engine rebuilt. I have had this vehicle serviced, oil changed regularly etc NOT ONE TIME has the oil pressure/low engine oil nor anything related to oil illuminated on my dash. CEL yes after it apparently was too late and damage was done which showed code P06DD And P0324 through OnStar Diagnostics. There are also other complaints with same issue, and no notification of oil /oil pressure issues with relatively low mileage that have led to engine rebuild. I still owe on this vehicle through GM Financial, and a $10,200 engine rebuild on top of that… Not what I would expect out of GMC~

2020 GMC TERRAIN. CONSUMER STATED THAT THEIR VEHICLE STARTED PULLING AND DRAGGING WHILE DRIVING.

The car has been in the shop for the turbo being over boosted four times and is getting hot, so they put thermo tape on the part, and now what if the car catches on fire? This is an electrical issue that needs to be solved.

Turbo failed. Car ran fine with no warning lights. Stopped at red light entering interstate and then could not accelerate which left us stuck in traffic. When it did move it would not shift and took over a mile to get above 20mph in a 65mph zone.

In January 2022, I purchased a 2020 GMC Terrain from a local GMC certified dealership along with an extended warranty. In July 2022, I started to experience intermittent acceleration issues. The issue only presented itself upon vehicle startup and was very sporadic. Upon startup, the vehicle was very slow to accelerate even with the gas pedal depressed to the floor. The vehicle would move at an extremely slow rate of speed for approximately 10 to 15 seconds before the vehicle would engage and actually start moving forward at the expected rate of speed. This would happen 4 to 5 consecutive times before things seemed to "warm up" and run smoothly. It proved to be dangerous at intersections if making a left hand turn into oncoming traffic or during heavy traffic times. From the beginning of July to Aug 9th, this has happened on 5 separate occasions. The story is the same, I start the car after it has been sitting for a bit (it's been from several hours to several days) and the issue will present itself without warning. There are no fault or error codes. I've taken the vehicle to my mechanic as well as the dealership where I purchased the car and both have run diagnostics on the vehicle with no luck. My mechanic did drive the car and he experienced the issue first hand but he could not figure out what was wrong. In the event other Terrain owners are experiencing this same sporadic acceleration issue with no fault or diagnostic codes, I wanted to make sure we documented our issue. I did not record the dates of the first few instances but the last two have been July 24th and August 9th.