2021 GMC SIERRA 1500 Complaints

The failed component is the engine coolant control valve on a 3.0L Duramax truck. The failure has been documented and confirmed by both an independent mechanic and an authorized dealership. The malfunction creates a significant safety hazard. Without warning, the truck will suddenly enter a reduced engine power mode while traveling at normal highway speeds. When this occurs, the vehicle will not allow acceleration beyond approximately 50 miles per hour. This is especially dangerous when operating on roadways with speed limits of 70+ mph, as the sudden and unexpected loss of power places myself and surrounding motorists at risk. The problem has been reproduced and confirmed by Steele GMC in Round Rock, Texas. In addition, the vehicle has been inspected by an independent mechanic, both of whom verified the coolant control valve failure. Prior to the initial occurrence of the failure, there were no warning signs. Once the malfunction occurred, the check engine light illuminated. General Motors has issued Service Bulletin #25-NA-185 (revised December 4, 2025), which addresses engine coolant control valve failures on 3.0L Duramax vehicles and outlines the proper diagnostic and repair procedures for this exact failure mode. This bulletin applies to 2021–2026 3.0L Duramax trucks. Additionally, GM has implemented Special Coverage program N252508341 for 3.0L Duramax coolant control valve failures, which extends coverage up to 15 years or 150,000 miles when diagnostics confirm the failure condition. Despite the fact that my vehicle’s documented failure matches the exact conditions described in the above-referenced service bulletin and special coverage program, I was informed by Steele GMC that my specific VIN is not included in the warranty. Given the documented safety risk, the confirmed diagnosis, and the existence of official GM guidance addressing this precise issue, I respectfully request this be reviewed and appropriate coverage or corrective action be authorized

I have had shuddering on the highway and a few hard random diwnshifts. Last week I went to start my truck and the transmission started grinding and rattling. I was told after towing to the dealer it needed a transmission due to pump not getting enough fluid and had failed. I was told I needed to pay, even though the part causing the problem had a extended 150,000 miles and the subsequent pump failure is a result of the control valve failure.

Had a P1098 code. The truck was diagnosed by a certified technician. Found to have a failing coolant control valve. GM has issued special coverage for this known failure. Special coverage is not including the VIN for this truck although it falls in the criteria for model, year, and engine model.

At 22,000 miles I experienced issues while driving on a 150 mile trip. We frequently take this particular drive. We choose to driver later in the evening to miss commuter traffic. This even we pull over for a late dinner and hear a loud ticking noise while the the truck seems to lose power. I turn the vehicle off and start it again and its worse, it barely idols and shuts down. I'm in a parking lot and drive down the block to a gas station where serves only gas and no mechanics onsite. I turn off the car and wait 5 mins and restart, same results but this time all the warning lights come on. We end up finding a hotel and in the morning i find a Chevrolet dealership down the block, I ask if I can take it in, there the advisor connects to my obd port and says there are many issues and needs to see a mechanic. I manage to get it towed 80's to the original dealership. Advisor says the engine is bad and replaces it. Now my vehicle has 38,000 miles and I run into the same issue, loud ticking sounds and low power. Immediately I drive it home and the next day have it towed to the dealership to have it looked at. The advisor said during their analysis they saw metal in the air filter so another engine has to ordered and installed.

The engine has been burning oil since purchased but really highlighted when at 47k miles I got a dashboard message saying “reducing power to engine” I checked the oil and it didn’t register in dipstick. I added 3quarts of oil to show up on dipstick. When I changed the oil which I did at my own garage only 2.5qrt came out including what was in filter. It’s since take an average of 2.5qrt between oil change at 7500. Also the transmission is slipping which happened after warranty expired at about 69k miles and I don’t want it to repair or repair until gm fixes these issues which they know are problem in2020-2021 models but they haven’t addressed it. My truck has been serviced at the dealership except fo 3 oil changes. The issue are noted but the answer is car burn oil typically between changes. Yeah they do if it was 20yrs old not 3yrs. The issue lies with GM. It’s Needs to be addressed.

Burns excessive amounts of oil between oil changes.All cars were covered under the g.M recall mine fell, one month behind.But this motor is the exact motor that has been recalled to put in a heavier weight oil.Please expand the recall.So my truck can go in.

The contact owns a 2021 GMC Sierra 1500. The contact stated while driving 65 MPH, the vehicle was shaking abnormally with the check engine warning light illuminated. The contact pulled over to the side of the road and had the vehicle towed to the residence. The contact referenced NHTSA Campaign Number: 25V274000) (ENGINE AND ENGINE COOLING) as a possible cause for the failure. A dealer was not contacted. The vehicle was not repaired. The manufacturer was not made aware of the failure. The failure mileage was 66,456.

My 6.2 engine locked up and left me stranded. Had it replaced with s new engine on 10/31/2025 and I'm having problems again with it. As well as my 10 speed transmission slipping and hunting for gears

The oil consumption is abnormal and burns almost 2.5 to 3 quarts between oil changes. This can be a heavy risk to the engine if I don’t check on it every couple weeks. I don’t think after the price I’ve paid for this truck that I should have this concern and this should not be the case

4 months after bring my truck back to the dealership for a body valve issue on the 10 speed transmission. The truck went into limp mode while I was driving.