2019 GMC Acadia engine problems

Filed Sep 18, 2026 · Engine · PA

I own a 2019 GMC Acadia equipped with the 3.6L V6 engine. VIN. See form above In 2025, the engine coolant thermostat failed on my vehicle and required replacement at my expense. I am submitting this complaint because I believe this may represent a recurring component problem affecting 2019 GMC Acadia vehicles and I would like the federal safety agency to determine whether the condition presents an unreasonable risk to motor vehicle safety. General Motors has published service information addressing thermostat-related conditions on GMC Acadia vehicles equipped with the 3.6L engine. GM has also issued special coverage for an engine coolant thermostat condition on certain GM vehicles. GM’s special coverage describes a thermostat that can open at a lower temperature than intended, resulting in a malfunction indicator/check-engine light and diagnostic trouble code, and in some cases causing the engine cooling fans to continue running after the vehicle is shut off. My 2019 Acadia uses the 3.6L engine and the thermostat assembly addressed in GM’s service information. Despite this, my 2019 model year is not included in the current extended thermostat coverage. There is also a second, independent occurrence involving the same model year. My father owns a separate 2019 GMC Acadia, and the thermostat on his vehicle also required replacement in 2026. These are two separate vehicles that experienced thermostat failures requiring replacement. I understand that a thermostat failure is not necessarily a safety defect by itself. However, I am concerned that a recurring failure of this component could potentially create a safety risk depending on the failure mode and resulting vehicle condition. I am therefore asking the federal safety agency to review the available consumer complaints, manufacturer service information, warranty data, and GM special-coverage actions to determine whether there is a safety-related defect affecting 2019 GMC Acadia vehicles equipped with the 3.6L engine.

Filed Sep 14, 2026 · Engine, Steering · LA

I am submitting this complaint to request that the federal safety agency investigate a potential safety defect involving the engine coolant temperature monitoring system, thermostat/engine coolant temperature sensor system, and its relationship to reduced steering assist in 2019 GMC Acadia vehicles. My 2019 GMC Acadia, currently at approximately 91,500 miles, has experienced the following symptoms: • The engine temperature gauge remains flat or reads abnormally low/cold. • The cooling fans run continuously at extremely high speed, creating a loud "screaming" fan noise. • The vehicle displays the warning message "Steering Assist is Reduced — Drive with Care." • The vehicle has a history of diagnostic trouble code P0128, "Engine Coolant Temperature Below Thermostat Regulating Temperature." I am concerned that these symptoms are related and represent a potential safety defect rather than an isolated thermostat or cooling-system repair. GM has issued bulletin PIT5967, "Service Steering Message With P0128," which applies to GMC Acadia vehicles from model years 2017 through 2023. The bulletin states that when P0128 is present, the ECM may be reading coolant temperature incorrectly and that a "Service Steering Message" may be displayed to protect the steering gear in the event of an undetected overheating condition. GM instructs technicians to diagnose and repair P0128 first. GM bulletin 17-NA-158 also describes a relationship between P0128, an invalid coolant-temperature signal, and the "Steering Assist Reduced, Drive With Care" warning. The bulletin explains that the steering module relies on valid coolant-temperature information to provide additional steering assistance under cold conditions. Also will not register when put in park. Getting error message "shift to park" take multiple restarts of the vehicle and shifting gear back and forth for it to register.

Filed Aug 17, 2026 · Engine · 81,126 miles · SC

The contact owns a 2019 GMC Acadia. The contact stated that while driving at an undisclosed speed, the engine seized, with several unknown warning lights illuminated. Additionally, the battery low and steering assist warning lights were illuminated. The contact's minor children were occupants in the vehicle during the failure. The tow truck assistant arrived. The tow truck driver assisted with restarting the vehicle. The contact was able to restart the vehicle. The vehicle was taken to Firestone; however, the failure was not duplicated. The contact stated that a portable diagnostic tester was attached, but no error codes were displayed. The failure reoccurred. The vehicle was taken back to Firestone, where it was diagnosed with a failed START/STOP module. The contact was informed about Technical Service Bulletin: 21-NA-139. The manufacturer was made aware of the failure but provided no assistance. The contact was advised to contact the federal safety agency Hotline to report the failure. The failure mileage was approximately 81,126.

Filed Aug 12, 2026 · Electrical, Engine · PA

See attached file

Filed Aug 3, 2026 · Engine, Transmission · 154,428 miles · NJ

The contact owns a 2019 GMC Acadia. The contact stated that while driving at an undisclosed speed, the transmission failed to properly shift gears and the vehicle failed to exceed 40 MPH while driving. The contact stated that the transmission failed to shift above third gear. The check engine warning light was illuminated. The vehicle was taken to an independent mechanic, who discovered that there was no transmission fluid inside the torque converter. The vehicle was scanned and displayed an issue with the transmission control module. The local dealer was contacted and confirmed that the VIN was not included in the federal safety agency Campaign Number: 20V668000 (Power Train). The vehicle was not diagnosed or repaired. The manufacturer was contacted and referred the contact to the federal safety agency Hotline to report the failure. The approximate failure mileage was 154,429.

Filed Jul 30, 2026 · Engine, Transmission · ME

I was at a red light, I went to drive as the light turned green and my car stopped and wouldn’t drive, I could go into neutral to get out of way but anything the car would stop. There is no codes or lights turned on my dash though.

Filed Jun 27, 2026 · Engine · PA

Shortly after purchasing my 2019 GMC Acadia with approximately 52,000 miles, the vehicle displayed a "Steering Assist is Reduced. Drive with Care." warning message and illuminated the check engine light with diagnostic code P0128 00 (Engine Coolant Temperature Below Thermostat Regulating Temperature). I disconnected and reconnected the battery, after which both the warning message and check engine light disappeared. However, the engine coolant temperature gauge then began behaving erratically. On multiple cold starts, the gauge would immediately indicate that the engine was already at normal operating temperature even though the engine had been sitting long enough to be completely cold. This led to a diagnosis of a thermostat and/or engine coolant temperature sensor failure. After researching the issue, I found many other owners reporting the same thermostat and engine coolant temperature sensor failures. I believe this is a widespread defect that should be investigated because incorrect coolant temperature readings can prevent the driver from knowing the true engine temperature and may result in improper engine temperature regulation, overheating, and possible engine damage.

Filed May 15, 2026 · Electrical, Engine · 48,500 miles · CT

The contact owns a 2019 GMC Acadia. The contact stated that while driving at an undisclosed speed, a “Steering Assist is Reduced ” warning message unexpectedly displayed. The contact also stated that the thermostat became inoperable. Additionally, the thermostat information was no longer displayed on the instrument panel. The vehicle was taken to the dealer, where it was diagnosed that the thermostat had failed and needed to be replaced. The vehicle was not repaired. The manufacturer was made aware of the failure and referred the contact to the federal safety agency Hotline for further assistance. The failure mileage was approximately 48,500.

Filed Apr 11, 2026 · Electrical, Engine · NE

The warning steering assist reduced, drive with caution appears. Shift to park appears. Temperature gauge drops to zero. Fan runs on high. A/C & heater don’t not work when this happens. We certainly do not feel safe driving our Acadia like this. Can’t trust that it won’t start on fire.

Filed Apr 1, 2026 · Engine · LA

My 2019 GMC SLT seems to be having sensor problems. I keep getting a message that my driver assist is reduced and my A/C only blows out hot air. It’s done this to me randomly id say about 4-5 times. It will go off as I’m driving and than my temp gauge goes to zero. I did research and alot of other users have the same issue and say thermostat or thermostat sensor. If I disconnect my negative on battery and wait a few minutes it will work again.