My GMC had a terminal engine failure around 5/3/25. This disengaged the ESC, parking brake, and driver assist abilities as well as making the truck undrivable. GMC service diagnosed the truck needed an entire new engine. The repair took over 2 months to complete and now that I have the truck back, the adaptive cruise control is not working.

- Belmont, MA, USA

Check engine light came on. Cooling fan for engine running none stop. Reduce power mode from engine. Took to dealer, said it-??s the coolant control valve. Dealer said the part is on back order and don-??t know when they will get it in. Looked up the issues and sounds like many people are having the same problem with the 3L diesel from GMC. These people reporting the same thing and having to wait months for the part. My truck was just out of warranty by 200-300 miles

- Dover, PA, USA

On June 19th, 2025, I was driving to work when my truck began to lose power, and the check engine light came on. The error on the display is Loss of Engine Power. I took it immediately to Oreilly's so they could run the free engine light check. When they got the report, the employee was amazed that there were over 45 problem codes showing up. As I drive the vehicle there is a pull back from the engine before it starts to pick up speed. On braking as well there is a little kickback before it comes to stop. It takes more foot pressure to pick up speed. The Truck using up more fuel because of this issue. I took the truck to a local certified mechanic, and he ran the diagnostics as well and it came up with the over 45 problem codes as well. His recommendation unfortunately was to take into the dealership so they could check it and see if they have a solution for this engine malfunction and error codes.

- Mcallen, TX, USA

Engine overheating at 50,000 miles. Temp would intermittently jump up to 230plus degrees while driving. Radiator replaced per dealership diagnosis. Issue still happening.

- Charleston, SC, USA

Woke up one morning and the entire back seat, entire truck flooring was soaking wet. Got it to Gerber collision in El Reno, Oklahoma. They said that the back window had a crack in it. My insurance said it is a mechanical issue on the sliding back glass and they do not cover such issue. Also want to turn in that the transmission in this truck had to be replaced two week prior to this incident. The truck only had 118,000 miles on it. Safe to say that this 10 point GMC diesel truck is a nightmare and the entire truck is a hazard. They need to take these truck off the market.

- Petal, MS, USA

The contact owns a 2020 GMC Sierra 1500. The contact stated that while driving on a main road at 40 MPH, the vehicle lost automotive power, causing the vehicle to shut off. There was no warning light illuminated. The vehicle was towed to a local dealer where the vehicle was diagnosed, and the contact was informed that the engine wiring harness was faulty and needed to be replaced. The vehicle was not repaired. The manufacturer was not notified of the failure. The approximate failure mileage was 80,000.

- Prairieville, LA, USA

The contact owns a 2020 GMC Sierra 1500. The contact stated while driving at an undisclosed speed, there was an abnormal knocking sound coming from the engine compartment before the vehicle lost motive power with the check engine warning light illuminated. The vehicle was towed to the residence. The dealer was contacted; however, the vehicle was not diagnosed or repaired. The dealer referred the contact to the manufacturer for further assistance. The manufacturer was made aware of the failure. The approximate failure mileage was 138,000.

- Moneta, VA, USA

I own a 2020 GMC Sierra 1500 with a 5.3 liter engine..... My engine lifters failed at 105,235 miles.... Lifter broke and damaged the Cam Shaft to a point that required full engine replacement costing me $10,800. When I asked GM for help, they denied because I went to a local repair shop with certified mechanics. I believe GM is fully aware of this problem and they are ignoring I think GM should pay for at least half of my repair bill. Thank you!

- Clemmons, NC, USA

Engine failure/ lifter issue with no prior warning. Driving down the road vehicle suddenly lost power and error message appeared. The vehicle was inspected by GM dealer and extended warranty company in late 2023. We no longer own this vehicle

- Nacogdoches, TX, USA

My engine slowed down on the interstate. My steering wheel was visibly shaking and I lost the steering access control. The truck threw an Cylinder 6 error code. At the mechanic, they identified that at least one of my camshaft lifters had failed. If I had continued to drive my vehicle, the engine block would have eventually locked up.

- Lexington, SC, USA

I took my 2020 GMC Sierra 1500 to the dealership after Cylinder #5 seized while driving, and I was forced to replace the entire engine. At the time, I contacted the dealer and was told there was no recall related to this issue. However, I have since learned that GMC has issued a recall for similar engine problems affecting 2021-?"present Sierra 1500 models, but not for my 2020 model year. I believe this issue may be related and would like further investigation and consideration.

- Thornwood, NY, USA

Vehicle currently has 104K and needs a 3rd engine. The same issue happened to the second engine as the first. While Driving the engine just stop working. They say it is a problem with the camshaft. Metal gets into the transmission and that also has to be replaced. A vehicle engine should not just stop working! Especially on an interstate. GMC refuses to add this engine to the recall list. However, I don't understand how the safety of families can continue to be placed in jeopardy.

- Evans , GA, USA

Transmission has slipped and shuddered multiple times. We have had it diagnosed at gmc dealership and our mechanic, advising that it is 8L90 transmission failure. It will slip to lower gear abruptly, causing for possible safety issues especially on the highways.

- Buford, GA, USA

1. On 05/9/25, the exhaust emissions system malfunctioned, triggering diagnostic trouble code P2C7A (exhaust emissions system failure). This repair, the seventh attempt since June 2024, addressed the same recurring emissions issue previously involving replacements of components such as the NOx converter (02/18/25, 03/13/24) and EGR valve (02/18/25). The vehicle is available for inspection upon request. 2. The P2C7A failure risks limp mode, reducing vehicle power unexpectedly, which is hazardous on highways, especially while towing. Exhaust emissions system malfunctions release excessive pollutants, posing environmental and health risks to others. 3. Yes, the P2C7A code was confirmed by dealer during the 05/9/25 repair, following prior confirmations (e.g., 03/31/25-?"04/05/25. 4. The vehicle was inspected by Young Chevrolet-Cadillac during multiple repairs (e.g., 03/31/25, 05/9/25). 5. Yes, the check engine light and OnStar emissions alerts appeared prior to the 05/9/25 repair, first noted ~June 2024 (P2C7A onset). Exhaust smell and reduced fuel economy were observed intermittently. Symptoms persisted post-03/31/25 repair, leading to the 05/23/25 service.

- Brighton, MI, USA

Loss of power steering. Loss of engine propulsion at high rates of speed. Engine would not start.

- Keswick, MT, USA

Hi I have always taken good care of my 2020 gmc Sierra 1500 at4 6.2 Kept up with its regular and recommended maintenance. I had no warning signs on the dash. So it surprised me that while on my way to work early one morning I was getting off the highway exit and the truck lost power, my steering wheel hardened and it posed a great threat to my life and others on the road, as it suddenly decelerated in a area where people are driving at accelerated speeds. The whole truck was loosing power and shaking hard as I attempted to steer it to a safe location on the side of the road. Had a mechanic inspect it and they determined The truck ended up with a seized engine. I have since not been able to use my truck for 8 months and still currently paying monthly payments of 1000 to pay it off.

- Alamo, TX, USA

Lifter failure at around 102-103k miles, was doing a random misfire and transmission studder ( due to the dfm system activating, cutting down cylinders to save fuel while driving, this was happening since approx 59k miles, dealership and gm was aware of it and they said it was normal, but that normal misfire turned into a failed lifter causing misfire and studder. I ended up replacing the lifters myself put solid lifters and a new camshaft that would eliminate the dfm system and studder, ran good no studder and random misfire, and now my crankshaft or oil pump is bad which I will remove motor to furthermore inspect. I-??ve read forums and stuff where people would get a lifter job done and then soon after couple thousand miles later the motor goes bad. The 5.3 motors have bad crankshafts, oil pump and lifters just like the 6.2lt motors. After the lifter and cam repair, it ran good for couple thousand miles shortly after My gmc threw an -??oil pressure low turn off vehicle code-??, turned off vehicle immediately and checked oil, verified oil was good. Gm will not cover it because of it being way out of warrenty when I had issues with random misfire around approx 70-78k miles, and to note that my cat converter went back when lifter failed aswell. Also to note that when the lifters fails it throws a speed reduced to 55 mph, traction off, steering assist reduced, and brakes reduced, this is a safety hazard and also it will drain the battery and cannot start it if you pull over on the side of the road and turned it off and on again to make it back home.

- Ozark, AL, USA

Misfire alerts causing major motor repairs

- Orlando, FL, USA

Transmission shurtting, jerks, and vibration, bad torque converter bubble and pelling paint. It feel likes engine is lossing power

- Santa Fe , TX, USA

My 5.3 engine spun a bearing on the crank. Same exact problem the 6.2 got recalled for. Now if I put a used engine in it-??ll cost me around $6,000.

- Petal, MS, USA