2021 GMC Sierra 1500 AT4 6.2L engine, Little over 15000 miles, Purchesed May 2021. Drivining down the interstate with out warning, engine starting making back fire sounding noise, with a noticeable loss of power, I requested On Star to do a vehicle diagnostics, no faults was reported, No check engine light, temp was normal, oil pressure normal. The noise was off and on at first and then remained constant. Fortunataly I was able to make it safely back to my residents. I parked the vehicle and did a scan code and it did not have any codes, I did a pending code scan and it had a P0300 code. I started the engine and the noise was louder at first and then got quiter after about 15 seconds of running the check enging light came on I shut the engine down and did another scan it gave me a P0302 code. I feel that the vehicle is unsafe to drive and could cause a accident if it locks up on the highway. I contacted GM and reported the issue, they said take it to a near by GM dealer, I told them that I felt the vehicle was unsafe to drive and they tried to contact me with road side assistance but I was unable to get anyone on the phone. I feel that GM is ingnoring a known issue and that this will result in accidents and possible loss of life.

- Pipestem, WV, USA

Prior to this incident I had lifter failure on my 2021GMC SierraAt 8464 miles, I was on my way to work and I heard a loud bang and I had to pullover off the highway, my dad had to come all the way out To get the vehicle because it had major engine damage and it was on a holiday so no one would come help me.The vehicle was in the shop for over a week getting these repairs done, upon receiving vehicle it had been a week and I received service four-wheel-drive messages on the dash.Trying to use four-wheel-drive after this was a no-go every time I push the button nothing would happen it would stay in two wheel drive.After this I made an appointment with the dealership for this issue to be fixed, as I was going to get readyTo leave again with the truck having no issues other than what I-??ve stated when I went to go start the truck nothing happened at all every light lit up on the dash and part of me thinks it-??s an electrical issue but the Other part of me thinks the motor is locked up. Also the lights would not shut off when I turn the vehicle off so I-??ll have a dead battery in the morning.

- Holly, MI, USA

Valve lifter defects. June, 2021: 7,619 miles: left side valve lifter defect necessitating need for valve, push rod replacement on left bank of engine November, 2021: 13,171 miles: right side valve lifter defecting necessitating need for valve and push rod replacement on right side of engine

- Marietta, OH, USA

a lifter went out. While driving on a turnpike going 80 mph the engine starting knocking. The truck had to be towed to a GMC dealership where they confirmed a lifter went bad. the truck is a v8 with 8,000 miles on. the dealership advised what the problem was and replaced 4 of the 8 lifters. No warning was given, as soon as the lifter went out there were all sorts of errors that started showing up including emissions issues.

- Broken Arrow, OK, USA

While driving on the highway my truck started to buck and had a loud engine knocking noise. Speed was greatly reduced so much so that I was going under 45 mph in a posted 65. The check engine light did not come on. While sitting on the side of the highway there was a severe engine knock only when the revs on the engine were increased. Oil pressure and cooling temps were as they should be. The next day on the way to the dealership the engine started knocking. This time the check engine light came on, speed was greatly reduced at this time. After about five miles the knocking stopped and the check engine light went out. The Dealership checked it out and stated the lifters were bad. It seems that this is a known issue with GM. I was told by the Dealership that there were two other trucks ahead of me with the same issue. Also, because this is such a prevalent issue with GM, they cannot keep up with the demand for parts. My Dealership is waiting for a head gasket. GM has known about the faulty parts for approximately two years, and they are only replacing some of the faulty, poorly made parts, hoping the other side of the engine will not develop issues and fail. I feel this is placing the driver and occupants at risk while driving down the highway and not being able to maintain posted speed limits, or just locking up and engine, and coming to an abrupt stop.

- Raymond, NH, USA

The truck has 7500 miles on it and the check engine light keeps coming on then goes back off. It is impossible to schedule service as the light goes off before it gets to dealer. The when driving the truck many times the check engine light will flash for a minute or so and then remain on steady. This is very frustrating and the dealer has found nothing. It has happened probably 10 times since the truck was new and continues now. The truck was just serviced and the dealer found nothing causing this.

- Arcanum, OH, USA

Driving the car it started backfiring and then the ESC light came on and the car engine seemed to become erratic as well as steering and braking error messages and the check engine started blinking. Very scary before I got it pulled over and very thankful I wasn-??t on the highway etc. I-??m seeing all the issues online sounds like the supposed fixes for the 2019 models having issues aren-??t solving the problem. I bought mine in April and 4 months later it-??s become unreliable.

- Georgetown, MA, USA

Bought GMC Sierra 1500 brand new. At approximately 2300 miles the engine light started blinking. I took it in and they said they couldn't find anything wrong with it. At 3700 miles it started again and I took it in. It has a bent push rod causing engine failure.

- Columbus, GA, USA

GM has a lifter problem that causes complete engine failure. When this happens the engine completely locks up rendering the vehicle completely shutdown. This is happening over and over in early stages of 2021 Chevrolet and GMC Vortec V-8s. Mine happened at 13000 miles on a 2021 6.2L GMC Denali, and GM is only fixing the problem partially and as I understand with the same defective product that just failed. Also it is known this failure likely will happen again as it is a design flaw. If this happens in the wrong traffic situation it will be very dangerous. I am very concerned. When my vehicle was towed to dealer they had 7 other 2021 complete engine failures just like mine waiting for repair.

- Bethel Springs , TN, USA

The contact owns a 2021 GMC Sierra 1500. The contact stated that while driving in inclement weather, the vehicle stalled without warning. The contact looked under the vehicle and saw that engine oil was leaking from a puncture in the oil pan. The vehicle was towed to the local dealer however, the cause of the failure was not yet determined. The manufacturer was notified of the failure. The failure mileage was 5,800.

- Troy, MI, USA

This is the second time I stop at the grocery store for about 15 or 20 min, get back in the car push the start, then the truck keep cranking with no start for about 20 seconds. Then I try second time and it fires up.

- Gresham, OR, USA

5300 miles and when you accelerate it knocks and or ticks, and loss of power all lights on dash came

- Weatherford, TX, USA

The auto stop feature on my truck is dangerous! there is no way to permanently disable it. When pulling into traffic from a stop, there is a significant delay for the car to restart and get moving! I have almost been in several accidents because of this. Forget the $20 in gas this junk might save someone over a year! it is dangerous

- Pembroke Pines, FL, USA

Returned home after some shopping. Parked truck in drive way. Approximately 5 minutes after returning home my wife saw truck smoking from under the hood. Within another minute or two there were visible flames coming from the back edge of the hood. We called 911. Within 5 minutes the entire front end of the truck was engulfed in flames. The fire department arrived and put out the fire but the entire front and cab of the truck was destroyed. Fire investigators determined fire started at back of engine compartment near battery. Vehicle was stopped parked in off condition. In my driveway. No mechanical problems were noticed on ride home and there were no panel alerts for problems.

- Troupsburg, NY, USA

The contact owns a 2021 GMC Sierra 1500. The contact stated that while driving at 60 mph, an abnormal noise appeared under the hood. Without warning an explosion occurred. The contact managed to veer to shoulder of the road get out the vehicle to check and see what the noise was. The contact noticed flames appeared by the rear wheel on the driver side. The contact grabbed the fire extinguisher and extinguished the flames. The fire department was contacted however no report was filed. The police were contacted but no report was filed. The vehicle was towed to quality Buick GMC, Inc (7901 lomas blvd ne, albuquerque, nm 87110 (505) 765 1300) where it was diagnosed and determine the engine was faulty that would be covered under warranties to repair. The vehicle was repaired. However, the contact feels unsafe driving the vehicle. The manufacturer was notified of the failure started and started an investigation. The failure mileage was approximately 2,800.

- Greer, SC, USA

While driving during winter conditions with temperature at 3 degrees on a residential street with limited traffic, the diesel fuel in the fuel filter gelled up which caused the vehicle to display reduce power mode and then immediately shut off and would not start. The vehicle coasted to a stop in the middle of the street while in traffic. The owners manual lists utilizing top tier diesel which I did. While additives are not normally needed in most states to fuel for freezing conditions evidently they are needed in Oklahoma. The fuel filter housing is the only place where the fuel gelled up, which appears to be a theme in most GMC diesel trucks and does not effect fuel in the fuel tank due to volume. GMC has done nothing to improve the design or increase insulation to the thin fuel filter housing. If I had been in fast traffic on the interstate it would have resulted in an accident and possible loss of life.

- Broken Arrow, OK, USA

The vehicle was bought brand new and was only driven for a week. It was in motion on the freeway when the engine started to sound noisier than usual, like that of an older truck. It was hard to notice on higher speeds on the freeway, but upon slowing down on curves, it got more obvious that something was really wrong because the noise sounded like something was loose inside the engine. There was no 'check engine' light or any other warning lights. Upon exiting the freeway, the engine shut off completely while in motion. Fortunately, I was able to pull in a parking lot and park it safely. The engine would not start safely after that, and 'check engine' activated. The vehicle is currently being diagnosed at a dealership. Last update was that the engine was being taken apart completely because they said it's definitely inside it.

- Medford, OR, USA