The contact owns a 2021 GMC Sierra 1500. The contact stated that the check engine warning light was illuminated and the vehicle failed to accelerate above 60 MPH. The contact took the vehicle to the dealer who diagnosed that the DEF tank had failed and needed to be replaced. The vehicle had not been repaired. The manufacturer was not made aware of the failure. The approximate failure mileage was 4,000.

- Gap, PA, USA

The contact owns a 2021 GMC Sierra 1500. The contact stated that after starting the vehicle, the check engine light remained illuminated and the vehicle would not properly accelerate while depressing the accelerator pedal. The vehicle was taken to the local dealer who diagnosed that the engine valve lifter was faulty and needed to be replaced. The vehicle was repaired. The manufacturer was notified of the failure. The approximate failure mileage was 11,000.

- Hot Springs National Park, AR, USA

While driving, when approaching speed of 40 mph, the engine begins to have dull shutter intermittently as though I am going over pot holes or rumble strips when I am not. Regardless of time or day or weather the truck has performed in this way. I have had it to the dealership twice for the issue. The first time they said they didn-??t feel anything and unable to duplicate the problem. The second time, the vehicle was with the dealer for several days trying to determine the other issue it was there for. I requested they again try to recreate the concern. The service assistance asked if I was willing to ride with the technician to see if I could point it out for him. In scheduled a time to do so, when I arrived, the technician was not there. I reside an hour away from the dealership. Making these round trips and getting no where with support or answers. When this happens, I become extremely anxious about the safety of the truck. Also- while 4 X4 is engaged, the truck has significant shutter when going up hill, as though the transmission is going to drop. The entire truck will violently shake.

- Hanoverton, OH, USA

Vehicle has less than 10,000 miles. Started making a loud noise and shuddering in the engine while at speed on the highway. Made it to dealer but was concerned we were going to break down before making it safely there. Service manager strongly suspects engine lifters (he drove it briefly with me and says this is a known issue with this truck & they currently have 3 other trucks in the shop with this same problem. He said parts are a 3-4 month wait and vehicle is not driveable, will break down, but couldn-??t say when - could be 10 minutes, an hour, or a day. This happened to me on 2/1/22, while out of town on vacation. An hour on the phone with GM and was passed around to 3 different individuals. GM would not provide a loaner vehicle - leaving me stranded out of state. I had to get a rental vehicle on my own, GM claims they will reimburse me for a portion of this after 6-8 weeks. GM will not tow the vehicle home to Virginia (vehicle is in NC). I had to turn in rental car once I returned home because I can-??t afford to keep paying for this on my own and it-??s not a truck, which I depend on. Dealer is unable to fully diagnosis and document until end of week 2/7 or early week 2/14 as they are very busy. Unacceptable on ALL levels.

- Gainesville, VA, USA

8 lifters in my vehicle needed to be replaced. While driving my vehicle (12/4/21), after the auto stop feature was activated my truck experienced a lack of power and hesitation. I then turned the truck off and upon starting it was making a knocking noise. I immediately checked the oil as I wanted to make sure there was oil in the engine. I had warning lights on the dashboard and drove it about 3 miles to the dealer to be repaired. While driving it to the dealer, it did not sound right and shook. I also experienced a lack of power and was concerned for the vehicle to stall out while in traffic. The dealership informed me this is an issue with the 2021 GMC Sierra with a 5.3L V8 engine. I had seen online that GMC issued a service bulletin to have the lifters replaced in the 2021 GMC Sierra that were on the lot before they were sold (early December 2021). If this is a known issue why weren't the lifters replaced in vehicles on the road before the ones sitting on the lot. 8 lifters were replaced by the dealership but there was a shortage of parts due to the nationwide problem. There were no warning lamps, messages prior to the failure. The only symptoms I had was shaking and lack of power as indicated above after the autostop feature was activated. I then drove about 2 miles and went into a store before coming out and having the loud knocking on startup followed by warning lights and messages.

- Saegertown, PA, USA

Can turn vehicle off while in gear (drive specifically). When you let off the brake, the truck acts as if it is in neutral. Discovered in my driveway when accidentally forgot to shift into park when I pulled in and pushed the stop button. Truck turned off, which would only expect if in park (or neutral), let off brake, and it began quickly rolling backwards as if it was in neutral. Fortunately the brakes were working, but had any children been riding a bike on the sidewalk or walking by, my truck may have hit them. Had I been more distracted and not noticed initially, it could have rolled into the road and hit my neighbors truck. This behavior can be reproduced every single time, and I can easily supply video.

- Lithia, FL, USA

Less than 300 miles on the vehicle and it has thrown an error code P2B60. Relating to the engine coolant flow control valve position sensor. I have taken it to my local GM service center and they cannot see me for weeks. As of this morning the check engine light has disappeared but my fuel economy has severely decreased. It seems suspicious and possibly dangerous that it showed a check engine light with a warning of reduction in engine power the night before and disappeared in the

- Canton, GA, USA

Famous lifter issue in the l84 engine. Hundreds of documented complaints and current class action lawsuit. I had to stop on a busy highway and it caused unsafe passing and irritated humans.

- South Haven, MI, USA

On 11/19/2021. While on the express way our truck started sounding really bad. We drove it slower to a gm dealer in Highland MI. They said we had a misfire. And there was nothing they could do at this time. We drove a little further and it got worse. We had to stop at a rest area. After dark and in the freezing weather. We had it towed to a dealer in Frankenmuth MI. Our truck has 11,800 miles. It has a diagnostics report of Valve lifter defects left bank. Starter had to be replaced. And now gm wants to only fix to affected bank. But on the unsold trucks they will repair both banks as stated in service bulletin N212353840. If we have one bad lifter they should all be replaced as for this not to happen again. As of 12/08 2021 it is still in the shop [XXX] Thank you INFORMATION Redacted PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6).

- Pinconning, MI, USA

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