general problems of the 2019 GMC Acadia - part 1

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.

Loss of steering assist code p0128 due to stuck thermostat.

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).

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.

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.

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.

Car stalls and transmission dies.

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.

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

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.

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.

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.

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

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.

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.

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.

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.

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.

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.

Code 0128 coolant temperature sensor failure triggered reduced lane departure assist.

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.

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.

The contact owns a 2019 GMC Acadia. The contact stated while the vehicle was parked, she noticed that the engine caught on fire with no warning light illuminated. The fire was put out by the chicago fire department and after the vehicle was inspected the cause of the fire was determined as a failure with the electrical system. A police report was filed with the chicago police department and a report was provided. No injuries occurred and no medical attention was needed. The vehicle was not towed. The dealer was contacted, and the vehicle was not repaired. The manufacturer was not made aware of the failure. The failure mileage was approximately 65,000.

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.

In August 2021, I placed my vehicle in park and pressed the vehicle on/off button and received a message on the dashboard that stated "shift to park", even though the vehicle was in the off position. I was unable to turn my vehicle completely off (remained in auxiliary mode) and unable to lock the vehicle. I took my vehicle to a Chevrolet dealer who notated the issue was inspected and verified with a repair procedure under TSB 19-na-206. The service record reads "this condition is caused by the park switch in the transmission control not pulling bcm signal low to electronically show part position. Removed and reinstalled transmission control, installed new shifter harness and added wire harness jumper". In February 2024, the repairs completed by the dealer failed again, and this time the entire shifter (transmission control) needed to be replaced. The TSB that gm has put forth does not "fix" the issue, just puts a temporary band-aid on the problem until the vehicle is out of warranty and the customer is forced to pay for the repairs themselves. Without the vehicle registering it is park, the vehicle stays active and the customer is unable to lock or secure the vehicle, putting the safety of the customer at risk. It is also unknown if the vehicle is actually in park, putting those around the vehicle in danger of getting run over.

Engine consuming extra oil due to failed piston ring. Also, may be the cause of a coolant failure code. Burning through excessive oil and check engine light came on. Also, prior to these warnings, I've felt hesitation when accelerating and when the car changes gears. I was told by a shop that I need a new engine. This causes a dangerous situation because the car could just stop working while driving or in traffic.

My 2019 GMC acacia slt would not go into park to allow me to shut off my vehicle. It ran for over an hour before it finally went into park. This was dangerous as I had a young child to pick up in a busy part of town and I had to leave it running to try to get help. With a 3 year old child this was crazy. This is not the first time it has done this. My car had a recall and whomever fixed it didn’t do it. I feel this needs to be fixed properly now.

The contact owns a 2019 GMC Acadia. The contact stated while driving at undisclosed speeds, the "steering assist - reduce speeds" message was displayed, and there was a loud roaring sound coming from the engine. The contact stated that the check engine warning light was illuminated. The failure recurred while the heat was turned off in the vehicle. The vehicle was taken to an independent mechanic where it was diagnosed with a faulty temperature gauge. The vehicle was not repaired. The manufacturer was not made aware of the failure. The failure mileage was approximately 80,000.

Vehicle is constantly giving “shift to park” error. The steering mechanism has also been compromised, and the vehicle makes persistent jerking motions with accelerating. This could be quite dangerous.

Thermostat gets stuck, generally in open state. Ac also is disabled in this condition, soft code (no mil) mentions "limited steering available" and temp gauge on dash goes to 0. Hard code eventually comes (solid check engine light on the dash). Code, mil, and temp gauge can be cleared and fixed by disconnecting battery negative terminal and reconnecting it, and it will run consistently for a while, though it will return. Online there are no thermostat modules for this engine available (3. 6l v6, also in Cadillac xt6, Buick enclave, and Chevrolet traverse) showing that thermostat replacement is widespread. Online forum searches also describe widespread thermostat issues for this engine, at roughly $1200 per fix. A reliable thermostat is critical for long-term engine functionality, and should not need replacement at half of design life (~75-80k miles). Though this one tends to fail open instead of close, overcooling of an engine still could have its own issues, and failing closed could lead to engine overheating.

The contact owns a 2019 GMC Acadia. The contact stated while driving 55 mph, the electric power steering (eps) warning light illuminated, displaying the message "steering assist might be inoperable". The contact stated that following the message being displayed, the vehicle overheated. After restarting the vehicle, the vehicle returned to normal functionality, but the failure had since become a regular occurrence. The vehicle was taken to the dealer, who diagnosed a failure with the thermostat. The vehicle was repaired. The manufacturer was notified of the failure but referred the contact to the NHTSA hotline for assistance. The failure mileage was 70,000.

For a few months I intermittently get an engine light on, the temperature gauge goes to zero, the ac stops working, and an error that driver assist in unavailable. This will happen for a fee days and return to notmal where everything is fine. This happens on and off again. I google searched this and it is a huge problem with GMC Acadias. I used an obdii scanner and get a p0128 coolant error when this happens even though the temperature is fine. I just recently went over the new car warranty and GMC will not tell me if this is covered or not.

When I put my car in park and try to turn my vehicle off I get an error message saying “shift to park. ” the problem is the car is already in park and I am unable to turn the off. I usually have to start the car back and drive back and forth before the car actually recognizes it is in park. Im concerned for my safety.

Steering assist reduced drive with care" displayed on screen when I was driving. The temp gauge stayed on c, heat works fine, happened for a few days.

Gear shift notification problem. Unable to turn engine off after receiving "shift to park" message and the gear shift is visibly in the "park" position. In addition, the doors would not lock. My wife was forced to stay in the unlocked running car in a store parking lot for 25 minutes, until the car just "turned off" on its own. Unsafe for a woman (or anyone) to have to do at 10:30pm. This puts drivers in a really vulnerable position. Vehicle taken to dealer Jan 30, 2023. Was told they were familiar with the problem.