2019 GMC Acadia

I am submitting this complaint to request that NHTSA 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.

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 NHTSA Hotline to report the failure. The failure mileage was approximately 81,126.

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 NHTSA Campaign Number: 20V668000 (Power Train). The vehicle was not diagnosed or repaired. The manufacturer was contacted and referred the contact to the NHTSA Hotline to report the failure. The approximate failure mileage was 154,429.

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.

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.