2020 GMC ACADIA Engine Problems

Engine coolant thermostat failed under 55,000 miles and had to have it repaired on my 2020 Acadia. The 2021 Acadia has a recall on the thermostat.

Steering Assist reduced drive with care message. This is an extremely common issue and should be a recall. ALOT of people including my dealer service advisor has this issue with their vehicle this message comes up fans kick on high a/c stops working and temp gauge stops working. It can be reset by unplugging battery or clearing the code.

The "Steering Assist is Reduced" warning came on the same time the engine thermostat display stopped working. Then the check engine light came on the same time the AC stopped working. At first I thought maybe it was just the battery, so I had that changed out. But the "Steering Assist" warning continued and the engine thermostat display was still stuck on "Cold" no matter what (note: the oil temp display still worked fine). Looking in to the problem, apparently a defective Engine Thermostat is a pretty common issue with this vehicle. Why isn't there already a recall on this? The risk of engine overheating is HUGE and dangerous. I called GMC and they want to charge and arm and a leg to fix it (the car has 47000 miles so is just out of warranty). I don't want to wait until there is an accident to have something done about this.

I own a 2020 GMC Acadia that has experienced multiple major mechanical failures within one year. In January 2025, at around 74,000 miles, the transmission failed completely with no warning or clear indication of what was wrong. The vehicle suddenly lost power while driving, creating a safety risk for me and my child. I was quoted around $12,000 for the transmission replacement initially before getting GM involved. GM covered all but approximately $3,600 out of pocket for me and also covered 100% of the timing cover replacement, which was found to be defective during the same repair. Now, at about 84,000 miles, the thermostat has failed, triggering the check engine light. This repair has not yet been completed and is estimated at around $1,500. My dealership informed me they keep thermostat parts in stock because this failure is so common on Acadias. There were no warning lamps or symptoms before any of these failures occurred. All repairs and diagnostics—including the current issue—were done at the same GMC dealership where I’ve always had my vehicle serviced on time. I’ve been a loyal customer and maintain my vehicle according to the recommended schedule. Despite that, I have faced repeated high-cost repairs on a 5-year-old vehicle with relatively low mileage, which has been financially and emotionally overwhelming—especially as a parent who recently lost employment. Having the transmission, timing cover, and now thermostat all fail in such a short time clearly raises concerns about the reliability, safety, and manufacturing quality of the 2020 GMC Acadia’s powertrain and engine systems. Given that GM has already covered most of the transmission and timing cover repairs and dealerships acknowledge frequent thermostat failures, this appears to be a systemic defect that warrants formal investigation.

My 2020 GMC Acadia has experienced significant transmission issues, including [slipping / shuddering / “Service Transmission” warnings / loss of drive]. The problem has been diagnosed as a torque converter/transmission failure. GM has acknowledged known defects and issued recalls for 2019–2020 Acadia transmissions related to missing bolts in the start-stop accumulator endcap, which can cause fluid leaks and lead to torque converter/transmission failure. Many other owners have reported similar transmission issues, suggesting a systemic defect with the 9-speed transmission used in these vehicles. Despite these known issues, GM has declined to provide assistance with repairs. This failure compromises the safe operation of the vehicle, and I believe it warrants further investigation and potential recall.

I'm not sure of the exact sequence of events here, but there are multiple exhaust leaks. One is a crack somewhere in the catalytic converter that is now leaking exhaust from the back of the engine into the passenger compartment. The other leak is at the point of a bracket which fastens the two front exhaust pipes together. At the time we first noticed an exhaust leak sound upon cold start, there were are around 58,000 miles on the car. Now a month later there are still less than 60,000 miles on the car. The dealership originally estimated repair costs to replace the catalytic converter and two front pipes at $3,200. When I had another service garage look at the problem, they asked why the GMC dealer wasn't willing to replace the catalytic converter under the 80,000 mile / 8 year warranty. When I raised this with the dealership, they said this was a "gray area" becasue they believe what happened was that the exhaust bracket at the front pipes failed first, which then caused the catalytic converter to crack. Ultimately, they indicated they would be willing to pay parts and labor related to the catalytic converter (approx $2,000) if we paid the other $1,200 to cover the front pipes. What I don't understand is why, when both Chevrolet and Buick have extended their front pipe warranties on comparable model years of the Chevy Traverse and Buick Enclave, which use the exact same part numbers for the catalytic converters and pipes to 150,000 miles/15 years, why GMC has not offered the same special coverage on the Acadia. Regardless of which cracked first, the front pipe bracket or the catalytic converter, there is likely an engine vibration/movement issue that casues the cracks, giving rise to exhaust venting into the passenger compartment. Since we have yet to be able to schedule the repair (catalytic converter was on back order), we can now only drive the vehicle with the windows down to lessen the exhaust smell. The Acadia deserves a Special Coverage Advisory on this.

Car keeps throwing Poo14 code for VVt sensor, I’ve replaced the sensors and checked wiring on the side of the road and no damage found, went online and read multiple complaints and recalls on the same issue I’m having with my car. I enter my vin and no recalls have been found. I have a 2020 gmc Acadia Denali 3.6l v6. As well and the rear view camera cutting in and out multiple times anlmost causing an wreck. and a system update didn’t fix the issue.

While i was driving a code came on my dashboard that read "Steering assist is reduced drive with care". Soon after my check engine light came on. I pulled over not knowing what was happening. I took it to the garage to have it looked at and the mechanic stated that there are over 1000 gmc customers with this same issue and that the thermostat is stuck open. Which may cause major malfunction or even blow the engine. I looked up recalls for my vehicle and there are none but gmc issued a recall on other vehicles for this same issue. How do I get help here?

Transmission Control Value issues. I was driving my car and RPM spiked up high and I coasted and there was no acceleration the rear wheel tires locked up and I felt a jerk. Placed the vehicle in park and pulled hand gear shifter into Drive and the vehicle shifted back into park by itself. Same thing happened on placing the vehicle in reverse. Like the car had a mindset of its own. Luckily I was only going 20 miles per hour this could have been a fatality. This vehicle is not on the recall list. It should be because they use all the same parts.

The electrical, engine, and A/C systems failed. First our A/C stopped blowing cold. A warning light came up and said that driver assist was not working properly, and temperature gauge went all the way down to cold and did not move after that. It appears 3 things were malfunctioning. I was afraid to drive it for fear of burning up the engine due to an engine cooling malfunction and the car overheating. The A/C stopped blowing cold air but was still blowing warm air. The steering system alert was on the dash but wasn't an issue. I called OnStar to diagnose the problem and they initially said they didn't see a problem but based on what I described it would be best to have it towed. I later got an email that an issue was detected, code P0128. I called my dealership and they also said to have it towed so they could check it. We were not in a position to have the car towed and for it to sit in the service department for 5 days (that was what their queue backup was like then). I took the car to a nearby shop to have it checked. Because I was afraid to drive it we I got it there by disconnecting the battery. A/C was blowing cold like Arctic air and the temperature gauge went back to normal. We got it to the shop (a few miles away) and they could not duplicate the issue due to the battery disconnection "fix". They said the car would be temporarily functioning per usual but the problem will come back again soon and to bring it back when it happens. It happened 2 weeks later (2 hours from home/stuck in traffic). We found an auto parts store and bought a wrench to disconnect the battery again to get home and all was good once we did that "fix" again. We have a service appointment to have it repaired. Two quotes I got were for $1600 and $2200. Temperature sensors/thermostats were suspected to be the cause of the issue. The auto shop stated they frequently see this issue (P0128) with GMC vehicles in recent years, even when they are only a few years old. Ours is 4 years.

Transmission gave out

The car has parking brake on unable to disable.Have to put in drive force the system to move. Same with reversing the car. Air bags not working. Seat belt restraint on when we are wearing them. Left turn signal failure. Steering limited caution sign on. ESC sign on. Engine light on. Transmission unable to shift soon light on. Traction lights on. ABS brake light on. Temp says -40 degree when 30 out. I’m finding this unsafe to drive. Call GMC that told me to start On Star diagnostic. Pull up at least 4 codes And today the transmission indicators came on. Not sure what to do. The car has low miles. But I have stopped driving as of today due to break down or serious malfunction while driving.

The contact owns a 2020 GMC Acadia. The contact stated that while driving at various speeds, the vehicle was shuddering. No warning lights were illuminated. The vehicle was taken to a local dealer, where it was diagnosed that the torque converter needed to be replaced. The vehicle was repaired; however, the failure persisted. The contact stated that while starting the vehicle, and while driving at various speeds, a buzzing noise was heard coming from the engine compartment. The contact also stated that while driving at an undisclosed speed, the vehicle stalled with the anti-theft system warning light was illuminated and the vehicle lost motive power. The vehicle was able to be restarted; however, the contact stated that unknown alarm chimes were heard. Additionally, the liftgate opened independently and various other unknown warning lights illuminated, and messages were displayed. The contact stated that the vehicle lost motive power and failed to restart. The vehicle was towed back to the dealer however, the cause of the failure could not be duplicated. The vehicle was not repaired and remained at the dealer. The contact was made aware that the warranty had expired. The manufacturer was not made aware of the failure. The approximate failure mileage was 2,000.

Mileage: 2,000

AUTO STOP enabled while stopped at a stop sign on an uphill incline, there is enough of a delay on restart that it lurches and jerks upon restart, cant be good for transmission and passengers. very much a nusiance.

I noticed for months it was downshifting hard but transmission department was backed up I scheduled in September for an appointment October 26 and that morning I received a call to reschedule because they were still behind and had another appointment for November 10th. The morning of the incident 1st it did not want to start it would only turn over. When it started the check engine light was on (I called service he asked if I could drive it and told me to bring it in). Within 10 miles of driving, the car started to slow down. When I pressed the gas the RPMs would go up but the car would not accelerate. I was on the interstate so I started to coast to the side. When I got to the other side of the rumble tracks the fuel gauge warning came on saying no fuel (even though I had half a tank which was verified through the service department) and the car came to an abrupt stop. Had I not gotten over when I did the car would have stopped on the highway. I tried to turn it on to move it farther off the road and it would not. It started to just turned over like it did when I originally tried that morning (all over the occurrences happened while I was on the phone with Adrienne who i contacted through the gm help line).