What 374 owners told NHTSA about the 2019 GMC Acadia Denali

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 ODI 11746957

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 ODI 11730600

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 ODI 11728659

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 ODI 11727676

Loss of steering assist code P0128 due to stuck thermostat.

NHTSA ODI 11726308

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 ODI 11725460

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 ODI 11722618

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 ODI 11721476

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 ODI 11720758

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 ODI 11716967

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 ODI 11701474

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 ODI 11701179

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 ODI 11701096

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

NHTSA ODI 11701100

Car stalls and transmission dies

NHTSA ODI 11699512

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 ODI 11692973

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 ODI 11684644

Last week, the coolant gauge , on our 2019 GMC Acadia, was reading below "C".... The "Steering Assist" warning was disabled on the on-screen display and the Air conditioning stopped working. Took the car to a mechanic, who read the codes.... Mechanic stated that all symptoms were based on a defective GM thermostat. The thermostat was "stuck-open" causing the "steering assist" to be disabled as well as the A/C from being disabled as well. It seems GM has updated the part since when the series of Acadia were manufactured. After getting it repaired, at of our pockets, we researched and noticed that thousands of other GM Acadia owners had the same exact 3 symptoms: (1) malfunctioning coolant reading (2) "Steering assist" disabled (3) a defective ("stuck-open") thermostat..... Symptoms were exactly the same for all parties involved. We have owned many vehicles never had a thermostat fail before 65k Miles.... It became a safety issue since the car disables the "steering assist" based on the thermostat being stuck open. Contacted GM corporate which stated unless a recall, there would be no compensation. GM needs to make it right for the thousands of GM owners whose car has the 3.6L engine In short, this is a major issue since the car's steering system is NOT working correctly We would like a recall to be initiated. Thank you.

NHTSA ODI 11677536

Shift to Park Vehicle does not recognize the gear shifter is in the park position. Vehicle does not fully shut down.

NHTSA ODI 11677164

My coolant thermostat went out, causing my AC and steering assist to stop working. I have spoke to multiple other people who have had this same issue with their GMC Acadia and I believe this should be a recall. It’s going to cost me $1200 to have this issue resolved.

NHTSA ODI 11670057

Component: Shifter Assembly & jumper harness Safety concern: Can't turn off vehicle - Carbon Monoxide poisoning, physical safety when parking not at home, as I would have to leave vehicle running... Message in dash was present when I brought vehicle to dealer. Dealer also replicated No inspection other than dealer. Part returned to me. Warning message has been coming on for past 60 days or so, progressively getting more frequent I receive a 'shift to park' message in telltale after I have shifted to park. At times, vehicle will not shut off until shifter is manipulated for several minutes. I have concerns that I cannot park vehicle in garage, if I cannot shut it off. GM is well aware of issue, but has yet to recall them. Dealer actually had replacement shifter in stock for a same day repair.. I was charged $778.98 for the repair, and GM's customer assistance center response to me simply was to file a complaint with NHTSA. My wife does not feel safe driving, as there is no guarantee vehicle will turn off. Dealer replicated issue when I brought to dealership. Dealer has replaced part and has them. Warning lights only appeared when problem reared itself, initially began about 60 days ago, but is not occurring on approximately 2 of 3 shut downs.

NHTSA ODI 11665699

While driving the thermostat will go to zero and the steering assist is disabled. I have read a lot of forums that this is a known issue. The only way to reset it, so we have A/C is to disconnect the battery and it will last a day or two and do the same thing.

NHTSA ODI 11662786

My 2019 GMC Acadia with 33,000 miles on it started to give me a notification to "Shift to Park" even though I had already shifted the vehicle into park. A "ding! ding! ding!" alarm wouldn't go off and the vehicle wouldn't turn off unless I repeatedly changed the gears until it read it was in park. This went on for a few weeks and got progressively worse. I read on a GMC forum that the vehicle could slip out of gear while driving and potentially cause an accident. My mechanic found the shifter assembly to be defective and replaced the entire Gearshift Lever Assembly. He said there was a plastic piece in the gearshift that snapped off and said this was an issue in the older models but thought GMC had fixed this issue by 2019. Unfortunately, I was past my 3 year / 36K mile warranty and had to fork over $1300 to have it repaired.

NHTSA ODI 11661704

Our 2019 was repaired back in 2021 for a "shift to park" issue. This same issue is happening again after 2 years of being repaired. We see that there is a major issue with GMC vehicles and there have been recalls for this same exact issue. GMC Coleman, Lawrence NJ is refusing to fix problem under a recall. We would like this to be covered or reimbursed.

NHTSA ODI 11636424

Code 0128 coolant temperature sensor failure triggered reduced lane departure assist

NHTSA ODI 11631676