2020 GMC Acadia engine problems

Filed Nov 4, 2026 · Driver assistance, Electrical · NY

Getting a message that says sterring assist is reduced drive with care. This is a know issue with gmc acadias. The engine coolant thermostat need replacing. This is a covered repair on 2021 and later models where recalls have been issued. It is safety issue and should be covered on this model as well. My car only has 37k miles on it.

Filed Sep 30, 2026 · Engine, Steering · AL

Engine thermostat not functioning properly, therefore the display stayed on cold and would not show temp. It also cause the fan to run fast to cool engine. The AC would not cool and reduce power steering assist error message comes on. This is a known problem by GM and there is a recall for this issue on many of these vehicles, other GMC and Cadillac vehicles. Our vehicle should be added to the recall list!

Filed Sep 21, 2026 · Engine, Transmission · VT

2020 GMC Acadia bucks/hesitates when I take off or slow down and speed back up. Mechanic looked at it can see engine is having random misfires. We have tried plugs, transmission fluid, looked at everything we could think of. The condition improves if I put into AWD but still exists and worsens for a period of time after it shifts back into FWD mode. My mechanic has done a lot of research and found that one possible issue was a stretched timing chain but since it is out of warranty I just couldn't afford to have them tear it down it is an enormous job to see if that was the issue. It also lines up with other known issues like the auto stop issues and possibly a fuel pump issue. I have seen many people complaining online about this particular issue but not many on here and no recalls on my vehicle regarding the known issues

Filed Sep 21, 2026 · Engine · MN

Engine thermostat not functioning properly, opening too early and not allowing engine to operate at proper engine temperature. Check engine light comes on, reduce power steering assist error message comes on, engine temperature gauge reads cold when vehicle has been running for an extended period of time. This is a known problem by GM and there is a recall for this issue on many of these vehicles, other GMC and Cadillac vehicles. Our vehicle should be added to the recall list.

Filed Aug 27, 2026 · Engine · CO

Engine coolant thermostat failed open. Resulting in reduced steering capabilities, and no AC.

Filed Aug 23, 2026 · Engine, Steering · NY

Received a power steering reduced notice when starting the car, noticed shortly after driving the temperature gauge had not moved from its resting position. A few trips later it still had not moved and the check engine light came on. Mechanic looked at it said it may be a sensor quoted $1k to fix. A few days later it randomly started working and the light went off so I did not have it fixed. About 4 months later the same code displayed on the dash with the same issues. This time I noticed the ac would not work either it only blew out hot air. Also the fan under the hood turns on as soon as the car is started. Been about 3 days and it started working again out of nowhere.

Filed Jul 12, 2026 · Electrical, Engine · CA

[Symptom & Safety Hazard] While driving my 2020 GMC Acadia 3.6L V6, the Driver Information Center displayed the warning: "Steering Assist Reduced, Drive With Care" (SARDWC). Steering effort increased abruptly, the engine temperature gauge dropped to cold/zero, and the HVAC system lost air-conditioning function. The warning and reduction in steering assist presented a safety hazard and increased the risk of a crash. [Diagnostic Findings] Vehicle diagnostics identified DTC P0128 - Engine Coolant Temperature Below Thermostat Regulating Temperature. A GMC Certified Dealer technician diagnosed a failed engine coolant thermostat housing assembly. [Manufacturer Information] GM documentation links DTC P0128 and invalid engine coolant temperature signals to the "SARDWC" condition. GM Bulletin 17-NA-158 states the “SARDWC” condition is caused by an invalid coolant temperature signal and the steering module relies on coolant temperature information for steering-assist compensation. GM bulletin PIT5967 directs technicians to diagnose and repair DTC P0128 when the warning message is present. In Oct 2025, GM issued N252508350 for 2021 Acadia vehicles equipped with the 3.6L LGX engine due to an engine coolant thermostat condition. My 2020 Acadia is part of the same generation vehicle platform and is equipped with the same 3.6L LGX engine. It experienced the same thermostat-related failure symptoms, including DTC P0128 and the "SARDWC” warning. [Reason for Complaint] I am filing this complaint because a thermostat-related cooling-system failure resulted in a steering-assist warning and reduction in steering assist while the vehicle was being driven. Moreover, GM issued N252508350 for 2021 Acadia vehicles equipped with the 3.6L LGX engine due to the same engine coolant thermostat condition, yet similarly affected 2020 Acadia vehicles are not included. the federal safety agency should investigate whether additional 2020 vehicles are experiencing the same failure sequence and resulting safety risk.

Filed Jun 22, 2026 · Engine, Transmission · CA

Thermostat and cooling sensor went out on my car. GMC issued a special coverage bulletin for 2021 Acadia since it's a widespread issue but not the 2020 (mine) which is also a widespread issue looking online. The repair is over $1000 and should be covered!

Filed May 31, 2026 · Electrical, Engine · NY

Thermostat issue causing check engine light as well as steering assist to be turned off. Fan constantly runs. Reset code and immediately is fine again for anywhere from a day to weeks but then happens again. Car is just out of warranty but seems to be common occurrence as there is a service bulletin for the 2021 model

Filed May 10, 2026 · Engine · TX

A common issue in GMC vehicles (particularly 2017–2020 Acadias) is a "Steering Assist Reduced" warning message triggered by a failed engine coolant thermostat that gets stuck open. This causes the engine to run too cold (P0128 code), causing the computer to reduce steering assist (which is dangerous) and run fans on high, also the air conditioner fails. I have seen many complaints about this and it seems to be a manufacturers problem. GMC put out a repair bulletin for the 2021 models with this issue. It's time to address these other years.