2021 GMC Sierra 1500: engine overheating

Filed Oct 15, 2026 · Engine · 110,900 miles · KY

The contact owns a 2021 GMC Sierra. The contact stated that while driving at 60 MPH, a reduced power mode warning message unexpectedly illuminated, and the vehicle unexpectedly entered limp mode. The contact stated that the temperature gauge indicated a high temperature and the vehicle was overheating during the failure. The vehicle was taken to the dealer, where it was diagnosed that the control valve had failed and needed to be replaced. The vehicle was not repaired. The dealer informed the contact that this was a known failure and escalated the issue to the manufacturer for further assistance. The contact stated that the failure was associated with Technical Service Bulletin (TSB) N252508340 and believed the repair should have been covered under warranty. The manufacturer was made aware of the failure via telephone and website. The contact was also referred to the federal safety agency for further assistance. The approximate failure mileage was 110,900.

Filed Sep 28, 2026 · Transmission · NY

The transmission overheats on this vehicle shutting the vehicle into “limp mode” this is extremely dangerous when at interstate/highway speeds and the vehicle slows it self down to a dangerously low speed and all other vehicles around are traveling at a high rate of speed, this has happened twice, it has also happened while in back roads and tractor trailers have had to swerve to avoid a collision.

Filed Sep 14, 2026 · Engine · 94,328 miles · NC

The contact owns at 2021 GMC Sierra 1500. The contact stated that while driving 60 MPH, the engine was overheating. The message "Reduce Engine Power" was displayed. The contact shifted to neutral to reach the dealer. The contact associated the failure with Special Coverage: N252508341; however, the VIN was not included. The dealer diagnosed the vehicle with coolant control valve failure, and the vehicle was repaired. The manufacturer was made aware of the failure and stated that the cost of the repair was not covered under the special coverage program. The failure mileage was approximately 94,328.

Filed May 23, 2026 · Engine · AK

While driving at normal highway speeds, I got a warning light for engine overheat condition and cooling fans came on. I also got a warning that the engine would go to reduced power. I reported this issue to my local GMC dealer. Was told that this was a comm problem with this engine however: my vin number indicated that this vehicle was not covered under warranty N252508341. I was advised to bring it in for a $250 diagnostic check and repairs could not be made for at least 2 months because of backlog. Took my truck to a local vehicle repair shop where they diagnosed a faulty coolant control valve and replaced it for me for $2388.43. Why did GMC desert me?

Filed May 5, 2026 · Engine · UT

Coolant control valve not working correctly exhaust fan on high all the time but is never overheating this has been going on for a week it shows there is a 150000 mile warranty on it but not for mine

Filed May 5, 2026 · Transmission · ID

Coolant control valve has failed and caused the check engine light to occur is available for inspection. Could cause the car to overheat and cause harm to myself or others Yes has been confirmed by dealer No GM has a special coverage out for the specific vehicle and model years for this vehicle, but are stating that my vehicle does not pertain to that coverage.

Filed Mar 22, 2026 · Engine · NC

I am filing a complaint regarding a catastrophic engine failure in my 2021 GMC Sierra 1500 equipped with the 6.2L V8 engine. While driving under normal conditions, the engine suddenly failed without warning and threw a connecting rod, rendering the vehicle inoperable. There were no prior warning signs such as knocking, overheating, oil pressure issues or even a check engine light. The vehicle has been properly maintained, including regular oil changes using manufacturer-recommended 0W-40 oil. This failure created a serious safety concern due to the sudden loss of power while driving, which could have resulted in a dangerous situation, especially at highway speeds or in traffic. I am aware that General Motors has issued a recall and/or is aware of similar failures involving the 6.2L engine in certain 2021 vehicles. However, my vehicle’s build date falls just outside the currently defined recall range, despite experiencing the exact same type of catastrophic failure described in those cases. My build date is 12/20 and the recall was issued for 3/21. Given the similarity of this failure to known issues, I believe this defect extends beyond the currently identified recall population. This raises concerns that additional vehicles, including mine, are at risk of sudden engine failure without warning. I am requesting that the federal safety agency investigate this issue further and consider expanding the recall to include additional affected vehicles outside the current build date range.

Filed Aug 1, 2025 · Transmission · UT

What component or system failed or malfunctioned, and is it available for inspection upon request? The Coolant Control Valve has stopped working. How was your safety or the safety of others put at risk? While driving the truck can overheat very quickly which can lead to dangerous temperatures as well as cause me to make an emergency stop on the highway to allow the truck to cool down. Has the problem been reproduced or confirmed by a dealer or independent service center? Yes, I have discussed with a dealership in person and independent mechanic who have confirmed the issue and confirmed it is a very common issue. So common that the only replacement part for the problem is backordered. Has the vehicle or component been inspected by the manufacturer, police, insurance representatives or others? No, they confirmed the issue without inspecting the vehicle because of how common it happens. Were there any warning lamps, messages or other symptoms of the problem prior to the failure, and when did they first appear? There were no warnings before the issue. The issue happened and then the check engine light turned on as well as a "reduced engine power" message.

Filed Jul 9, 2025 · Engine · LA

Replacement part needed is COOLANT CONTROL VALVE according to diagnostics at local GM dealer service department after noting check engine light was on. YES, it is available for inspection. Told unsafe to drive as it would very likely overheat or worse. It has been in the shop for a month (as of June 11, 2025) awaiting a backordered part, which we’re told is a national backorder. No loaner vehicle available and told by service department that they have had another truck in for same problem for several months and that this problem is very common. PLEASE HELP us with getting the part needed!

Filed May 11, 2025 · Acceleration, Fuel system · NJ

The engine coolant flow control valve position sensor is faulty. I brought mt truck in to my dealership and I have been waiting for over a month to get the issue fixed because “the part is on backorder”. This issue makes my truck sound like a jet engine because it makes the truck think overheating and causes the fan to come on at full blast. After drivinf for awhile it goes into “ reduced engine power mode” which is totally unsafe because it reduces the horse power to that of a lawn mower. It takes about 30 seconds to get from 0-60, so merging onto freeways or in conditions where you need extra speed its completely useless and increases the scenario of being rear ended, immensely.

Filed Mar 27, 2025 · Transmission · NY

I own a 2021 GMC Sierra 1500 Duramax diesel. At around 60,000 miles, I received an engine coolant system alert through OnStar and retrieved a P1098 trouble code, which indicates a failure in the coolant control valve. This issue causes the engine fan to run excessively, creating loud noise, reduced fuel economy, and possible drivability concerns. After researching owner forums and talking to multiple service departments, I discovered this is a widespread problem among 2020–2022 GMC/Chevrolet Duramax 3.0L diesel owners. In many cases, the coolant control valve is failing prematurely, and the replacement part is on national backorder, suggesting a high failure rate. GM has not issued a recall or service bulletin to address the issue, and many customers are being told to pay out of pocket despite the systemic nature of the failure. This component is tied to engine temperature control, and failure could pose a safety risk if the engine overheats or derates unexpectedly. I am filing this complaint to document the issue and request the federal safety agency investigate this as a potential defect.