2020 GMC Acadia: check engine light

Filed Sep 21, 2026 · Engine · MN

Engine thermostat not functioning properly, opening too early and not allowing engine to operate at proper engine temperature. Check engine light comes on, reduce power steering assist error message comes on, engine temperature gauge reads cold when vehicle has been running for an extended period of time. This is a known problem by GM and there is a recall for this issue on many of these vehicles, other GMC and Cadillac vehicles. Our vehicle should be added to the recall list.

Filed Aug 23, 2026 · Engine, Steering · NY

Received a power steering reduced notice when starting the car, noticed shortly after driving the temperature gauge had not moved from its resting position. A few trips later it still had not moved and the check engine light came on. Mechanic looked at it said it may be a sensor quoted $1k to fix. A few days later it randomly started working and the light went off so I did not have it fixed. About 4 months later the same code displayed on the dash with the same issues. This time I noticed the ac would not work either it only blew out hot air. Also the fan under the hood turns on as soon as the car is started. Been about 3 days and it started working again out of nowhere.

Filed May 31, 2026 · Electrical, Engine · NY

Thermostat issue causing check engine light as well as steering assist to be turned off. Fan constantly runs. Reset code and immediately is fine again for anywhere from a day to weeks but then happens again. Car is just out of warranty but seems to be common occurrence as there is a service bulletin for the 2021 model

Filed May 10, 2026 · Engine · MI

Coolant temperature sensor failed - it is still in the engine. the fan stays on high all the time. And the AC does not want to turn on. The car is extremely hot to drive in during the summer months. I have to transport persons who are seniors and in their mid 80s. It is not safe to drive this car in the summer. I can't tell if its over heating or what is happening. The coolant temperature gauge does not work. The dealer said my car is out of warranty and that the AC will not start until the sensor is replaced. I said that it has less than 50,000 miles. They will not help me. The vehicle has not been inspected anyone other than the service mechanic. The engine light start coming on about a month ago. I drove first to an autoparts store to see if they could help. this is the first time I learned that it could be a bad sensor.

Filed Apr 30, 2026 · Engine, Fuel system · 61,699 miles · ID

The contact owns a 2020 GMC Acadia. The contact stated that while driving the vehicle, it stalled after initially adding fuel. Even though the reading indicated there was 1/8 of a tank of fuel. The fuel gauge failed to move. The thermostat was stuck open. The electric steering was not working properly. The engine light was illuminated. The traction control was turned off. The contact stated that the failure was related to the federal safety agency Campaign Number: 20V639000 (Fuel System, Gasoline). The contact stated that he was a master mechanic. The contact called the local dealer, but the vehicle was not diagnosed or repaired. The contact called two other local dealers, Tadd Jenkins Chevy 409 Farnsworth Way, Rigby, ID 83442, and Smith Chevrolet. Address: 3477 Pioneer Dr Suite 200, Idaho Falls, ID 83402. The manufacturer was contacted, but no assistance was provided. The failure mileage was approximately 61,699.

Filed Mar 6, 2026 · Engine · WI

Check engine light codes: P01F0; P0128 Engine coolant thermostat opening at a lower temperature than intended. Replace thermostat.

Filed Feb 12, 2026 · Engine · MI

Failed component was thermostat and I do not have possession of it. Over several months, I would receive infrequent and unrepeatable messages of "steering assist reduced" and my temp gauge would drop all the way to the cold side. No other recorded codes were being set after frequent trips to Autozone for verification and there were no check engine light warnings. No other signs of vehicle malfunctioning were present either. Recently, a code was finally set P01F0, so I had something tangible to take into shop as the prior condition was not repeatable. Hoping it was only the coolant temperature sensor, then ultimately learned the thermostat had failed - the much more expensive repair option. Seeing this complaint relatively frequently with the 3.6L engine on the federal safety agency. Plus, the tech says he has changed at least 100 of these - Acadias, Traverses, Enclaves, etc., any GM product with this engine and poor design/position for the thermostat.

Filed Nov 21, 2025 · Engine, Steering · AZ

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.

Filed Nov 3, 2025 · Engine, Transmission · IL

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.

Filed Sep 25, 2025 · Fuel system, Transmission · NJ

Vehicle will shutter or buck at variable speeds like, 35-38 mph, 40-45 mph and so on. if I take my foot of the gas and reapply it will shutter buck again at almost any speed. I took it to a mechanic and there are no codes, no check engine light. Shop recommended changing the transmission fluid so we did. Car still responds the same way, shutters and bucks when reapplying fuel pedal or slow acceleration.

Filed May 1, 2025 · Engine · NY

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?

Filed Mar 24, 2025 · Brakes, Fuel system · MI

The vehicle stalls when air start kicks on so when stopped auto stop kick on and when your ready to go the go stalls to turn back on. I have also lost power to the car randomly. Power train issue on car keeps coming on with engine light. I have taken to dealer when car was under warranty and they were very dismissive to my issue. They changed some sensor under warranty And they said the issue was fixed. But the issue remains and it’s causing several issues to the car with Also a fueling code to the engine light