GMC Sierra 1500 overheating problems

Filed Oct 26, 2026 · Electrical, Fuel system · KY

My truck has experienced recurring diagnostic trouble code P244B on [XXX], [XXX], and [XXX], 2026. The latest occurrence included a check-engine warning and reduced engine power. On [XXX], at 40,833 miles, Neil Huffman Chevrolet GMC in Frankfort, Kentucky, diagnosed a damaged diesel particulate filter differential-pressure sensor connector. The dealership's written estimate states that the connector had shorted, begun melting, and had broken wires at the back of the connector. I am concerned about the cause of the electrical overheating, the possibility of additional wiring damage, and the risk of unexpected reduced engine power while driving. I have also experienced intermittent transmission-related warnings and communication fault codes, although I do not know whether these problems are related. I understand there are GM technical bulletins addressing wiring-harness damage on certain 3.0L Duramax vehicles. I am not claiming these bulletins establish the cause of my failure, but I would appreciate having my experience evaluated for a possible safety-related defect trend. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

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 Sep 1, 2026 · Engine · 34,000 miles · TX

The contact owns a 2022 GMC Sierra 1500. The contact stated that while driving approximately 65 MPH, the transmission shifted to neutral(N), and the contact was unable to control the vehicle. The vehicle was coasted to the side of the road, and the transmission failed shift into park(P), reverse(R), or drive(D). The message "Conditions no Longer Exist for Driving," was displayed on the screen. The vehicle was towed to the dealer and was diagnosed with engine failure. The contact was informed that the engine needed to be replaced. The contact was informed that the nuts were welded to the engine, causing a failure with the engine overheating. The failure also occurred while driving 65 MPH, and the transmission shifted into neutral with the same message displayed on the screen. The vehicle was towed back to the dealer, and it was diagnosed with engine failure. The contact stated that the engine was replaced. The dealer informed the manufacturer of the failure. The failure mileage was approximately 34,000.

Filed Sep 1, 2026 · Engine, Fuel system · CA

I am reaching out to the federal safety agency due to a vehicle that I believe will get me and/or my family in a major accident and cause serious injury or death. The vehicle that I had purchased in 07/08/2025 had a clean history report and was bought at 54,587 miles. It started having issues 8,563 miles later (odometer reading 63,150 ) on a trip that was 400 miles round trip. I was driving the vehicle on a highway at 65 mph and i felt a knocking vibration in the pedal it was not long before i could even pull over when the engine throttle had completely lost power causing the vehicle to almost come to a complete stop immediately having to steer onto the shoulder. after failing with no check engine light or warning present during the use of the vehicle on the road. it was giving off high temp/engine overheating with the engine making a continuous knocking sound in the engine. It eventually seized to work completely not being able to shift into neutral to push, and had to get it towed to the dealership 204 miles away. GM had advised the dealership to replace the whole engine which they did, and that second engine had given out 678 miles later (odometer reading 63,828.) I am now on my THIRD engine and i cannot trust or rely this vehicle for saftey or transporation. i have reached out to GM to file a claim and attempt to adress this issue to try and come to a resolution, however they denied my claim and have said that i am not "eligible" for a buyback program. I am considering getting legal attorney this is very frustrating to say the least GM is a terrible manufacturer for this issue

Filed Aug 27, 2026 · Electrical · NE

I pulled up to a local store and parked. Just as I was getting out I saw smoke coming from the upper seatbelt area of the rear drivers side seat inside the cab. I jumped in back to see if there was a fire. As I was trying to pull out the top cushions of the interior roof, trying to locate a possible fire, the rear driver-side window suddenly "exploded" - broke in a web pattern across the entire window. I then broke out the center of the glass in case a fire started. I could smell a burning scent. The, suddenly the rear passenger-side window exploded in the same web pattern across that entire window. When my wife arrived to pick me up she could also smell the scent of burning wire. After researching the internet for this issue, we found out that this is a known issue. We discovered at least 6 websites describing this exact issue - one being a GM Customer Satisfaction Program #N192265660 dated January 2020. Apparently the component that has been determined to have failed is the rear window defrost (particularly in models with an electronic sliding rear center window) overheats and causes the smoke and the window breakage. After our truck being at the dealership for approximately 1 month while GMAC supposedly researched the issue, we received word today verbally (Aug 27, 2026) that they declare this issue is not a manufacturer's defect, and they will not cover the repairs. We have requested written confirmation and haven't yet received it. Not only do we currently have the original warranty on this vehicle, we also purchased the extended warranty for the vehicle. The vehicle was inspected by the dealership from which we purchased the vehicle and they stated they couldn't find any issue that would create the damages that the vehicle incurred. Prior to the incident there were no warning lamps or symptoms of any problem.

Filed Aug 25, 2026 · Engine · WY

Truck milage at the time of engine failure was 9,101. Well past the break in period for towing. We were towing a car trailer 2,000 pounds less the max towing capacity for the truck and going less than the posted speed limit. The truck was also in tow haul mode. The truck dash flashed oiled heating hot. We tried to pull over on the highway then the truck lost all power and overheated. Our trailer was not all the way off the highway, so a WY State Trooper pulled behind us and kept his lights flashing for 3 hours until a tow truck came. Truck could not be placed in neutral, so it had to be dragged onto the flat bed ramp of the tow truck. Truck was towed to the Gillette WY GMC dealership that same day. On Monday we were informed that the engine failed and needed to be totally replaced. The GM dealer cannot tell us how long it will take to get the new engine or how long we will be without the truck. This is the 6.2 V8 which GM assured buyer's of 2026 vehicles that the engine failures reported on previous year vehicles had been rectified on the new models. Less than 10,000 and the engine failed.

Filed Aug 24, 2026 · Engine · FL

I purchased my 2020 GMC Sierra 1500 AT4 with the L87 6.2L V8 new from a GMC dealer in March 2020 for $65,910 (VIN [XXX]). The truck has primarily highway mileage, very little towing, and has been well maintained. At 166,634 miles on [XXX], the truck developed a flashing check-engine light. The GMC dealer diagnosed “Cyl 3 lifter failure with camshaft damage” and determined that replacing the engine was preferable to repairing it because of the vehicle's mileage. The dealer installed a replacement OEM GMC engine and replaced both broken engine mounts. The replacement engine and installation cost $11,778. The replacement engine has subsequently required multiple repairs. At approximately 170,411 miles, the GMC dealer documented an exhaust leak that had occurred since the engine repair and a coolant leak from the upper radiator hose; both were repaired. At approximately 187,699 miles, the truck experienced overheating, coolant leakage, and loud engine-area noise. The dealer found that the water pump was coming apart and replaced the water pump and related components. I am reporting this vehicle because it is a 2020 Sierra equipped with the L87 6.2L engine and experienced catastrophic lifter/camshaft failure requiring complete engine replacement, followed by multiple engine-related repairs. I believe this history is relevant to the federal safety agency's investigation of L87 engine failures in earlier model years and warrants consideration when evaluating whether the known L87 engine defect extends beyond the vehicles currently covered by the recall. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Filed Aug 11, 2026 · Engine, Steering · NC

Head gasket failure and overheating. After fixed, power steering has just failed during driving. Will have to have it towed to shop