2019 GMC Acadia Engine Problems

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 NHTSA 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 NHTSA 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.

NHTSA ID

11765267

Incident

Apr 12, 2025

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.

NHTSA ID

11764000

Incident

Aug 1, 2026

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.

NHTSA ID

11757418

Incident

Aug 14, 2026

Mileage

81,126 mi

See attached file

NHTSA ID

11756510

Incident

Aug 8, 2026

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.

NHTSA ID

11754373

Incident

Jul 4, 2026

Mileage

154,428 mi

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.

NHTSA ID

11753750

Incident

Jul 30, 2026

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.

NHTSA ID

11746957

Incident

May 10, 2026

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 NHTSA Hotline for further assistance. The failure mileage was approximately 48,500.

NHTSA ID

11738131

Incident

May 15, 2026

Mileage

48,500 mi

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.

NHTSA ID

11730600

Incident

Apr 10, 2026

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.

NHTSA ID

11728659

Incident

Mar 20, 2025

2019 GMC Acadia message: Action Required Steering Assist Is Reduced Drive with care Both power steering and AC affected, check engine light on, engine temperature gauge off

NHTSA ID

11727676

Incident

Jan 10, 2026

Loss of steering assist code P0128 due to stuck thermostat.

NHTSA ID

11726308

Incident

Mar 10, 2026

My Acadia keeps an error message of "Shift to Park" this has been happening on and off for about 8 months. Now it goes on every time I try to shut my car off. I have to stop and start it up to 20 times before it shuts off. I am concerned that I may be somewhere and won't be able to turn it off. I know there have been recalls for this and I need this repaired. It's obviously a flaw on GMC and honestly, I should not have to pay for it. At this point, the car is only used close by my home. I don't feel safe using it. Please help. Not only me but all drivers affected. Thank you

NHTSA ID

11725460

Incident

May 1, 2025

Owner of a 2019 GMC Acadia Denali (VIN: [XXX] , current odometer ~87,164 miles), purchased new. In early February 2026, the check engine light came on. Independent diagnostic scan confirmed persistent P0420 code (“Catalyst System Efficiency Below Threshold Bank 1”) as current, history, pending, and permanent. Inspection showed the front exhaust pipe bracket had snapped, damaging the flex pipe and causing an exhaust leak. This failure mode directly triggers the P0420 code and requires replacement of the bracket and affected flex pipe section. This is a known recurring issue on GM’s Lambda-platform vehicles (shared platform, 3.6L V6 engine, and exhaust system design). GM Special Coverage Adjustment N212356540 covers 2019 Chevrolet Traverse and Buick Enclave models for front exhaust pipe bracket separation (resulting in pipe damage, holes, leaks, rattling, or efficiency codes), providing free repair for 15 years or 150,000 miles from in-service date, regardless of ownership. The failure on this Acadia is mechanically identical, yet the model is excluded from coverage despite matching part design and numerous similar owner complaints documented on NHTSA and BBB reports. Multiple attempts were made to resolve through the selling dealership (no response to service inquiries). Matter was escalated to GM Executive Resolution. GM required a redundant diagnostic scan at an authorized dealer (additional cost incurred), despite independent confirmation of the issue. GM ultimately denied any coverage, TSB applicability, goodwill assistance, or further support. The snapped bracket and resulting exhaust leak can produce noise, fumes in cabin, potential component damage, and emissions noncompliance via false/legitimate catalyst efficiency codes. Inconsistent application of coverage for the identical defect across equivalent Lambda-platform models raises concerns about a widespread safety/emissions issue affecting 2019 GMC Acadia. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

NHTSA ID

11722618

Incident

Feb 20, 2026

My car will be in park and it always says shift to park when its in park , this is very unsafe. Also when I change gears from park to drive or reverse the RPM revs up gets stuck then drops quick causing the hesitation and then kicks in.

NHTSA ID

11721476

Incident

Jan 2, 2025

My 2019 Acadia often will not turn off because it has a Shift to Park issue. Apparently it is caused by a faulty microswitch in the shifter assembly that fails to signal the Body Control Module when in park, leading to a persistent warning message, inability to turn off the vehicle and battery drain. It has been going on for at least 4 years. It appears there is a recall for this problem but when I search my VIN number a recall does not come up. There are many posts that say "certain" models in years 2017-2019 but why not mine? It is definitely a safety issue because it does not turn off.

NHTSA ID

11720758

Incident

Feb 1, 2022

Vehicle experiences multiple simultaneous failures including “Steering Assist Reduced / Drive With Care” warning, extremely loud cooling fan operation, temperature gauge not functioning, tire pressure monitoring system failure, and widespread electrical issues (windows, mirrors, infotainment delay). Issues occurred together and are consistent with numerous owner reports for 2019 GMC Acadia models. Condition affects steering assist and engine temperature monitoring, creating a potential safety risk.

NHTSA ID

11716967

Incident

Jan 26, 2026

Check Engine Light came on with message of "Steering Assist is Reduced Drive with Care". This same thing happened to my sister-in-laws 2019 Acadia 2 months earlier. Took it in right away to the dealership to find out it's the thermostat, it's a common/known issue and it isn't covered under my extended warranty and will cost ~$1300. I'm seeing this is a common issue for Acadia's and has not had a recall, don't understand why. It's one thing if this is a easy part to replace, but GM has made it so that most people now need a dealership or auto repair shop to fix it.

NHTSA ID

11701474

Incident

Nov 17, 2025

I'm going to have to replace my thermostat and most likely my sensor. It will pop up saying (steering assist is reduced drive with care) my temperature gage on my dash will sometimes will not go up, my heat is acting funny. I've had also when I put it in park saying it's not actually shifted into park.

NHTSA ID

11701179

Incident

May 1, 2025

Thermostat is repeatedly going bad. Throws Steering Assist reduced. Had it replaced twice and it’s bad again.

NHTSA ID

11701100

Incident

Dec 31, 1969

I bought a car about 2 months ago and they did not tell me the thermostat was bad and they won’t cover it.

NHTSA ID

11701096

Incident

Sep 10, 2025

Car stalls and transmission dies

NHTSA ID

11699512

Incident

Nov 10, 2025

The contact owns a 2019 GMC Acadia. The contact stated that while driving at an undisclosed speed, the message "Steering Assist Fault - Drive with Caution" was displayed. The vehicle was taken to an independent mechanic, who retrieved DTC: P0128 (Engine Coolant Temperature Below Thermostat Regulating Temperature) and replaced the engine coolant thermostat. The manufacturer was made aware of the failure and advised the contact to file a complaint with the NHTSA Hotline. The failure mileage was 55,114.

NHTSA ID

11698972

Incident

Oct 25, 2025

Mileage

55,114 mi

Due to negligence of gmc wright of wexford during the replacement of 3rd new transmission they did not clamp a hose together causing coolant to leak and my thermostat to come on n off. Causing further damage to my vehicle

NHTSA ID

11692973

Incident

Sep 1, 2025

Unknown My 2019 Acadia Denali has/is been repaired 6 times in 1 1/2 years for engine oil leaks , has had transmission repairs twice , radiator repair and replacement. Also suspension warranty work as well . I feel the oil leaks is and has been excessive and dangerous due to no warning lights never displayed to alert me to check oil

NHTSA ID

11684644

Incident

Aug 27, 2025