After 2 years of owning the vehicle, after every oil change, it would indicate low oil just before an oil change causing for us to add an additional a quart of oil to keep it running smoothly. We informed the service technician of the situation on multiple occasions and no further inspection was completed, and just an oil change was serviced. After a few months we noticed the engine was running rough and a white smoke coming out of the exhaust on acceleration then the check engine light came on. We brought the car to get tires replaced and to service the check engine light, the technician stated that the check engine light a failure in the catalytic converter. We brought the vehicle to the local GMC service center, where they indicated that the we required a replacement engine because of catastrophic engine failure. We reported that the check engine light was due to catalytic converter failure. The service technician ensured that the priority was the replacement of the full engine not indicating what was the main cause of engine failure stating that the catalytic converter could have led to the failure of the engine as well. We replaced the engine, and after 3 months of vehicle being in the shop the engine was replaced. Three days after receiving the vehicle, a check engine light came on. We did not drive the vehicle until we had to return it back to the service center. The service technician stated that it is due to a lack of communication from the engine to the ECU. The technician called the following Monday stating that the check engine light was due the catalytic converter. We told the technician that was the primary reason that the customer the vehicle in the first place. We asked if there was an alternative to replacing the catalytic converter since we already paid 12k for the engine replacement. We asked if they had taken apart the catalytic converter to confirm its not a sensor issue. They replied that the codes indicates its the whole converter.

- Parrish, FL, USA

[xxx], I purchased a 2021 GMC Sierra 1500 from faulkner Chevrolet in bethlehem, pa. I test drove the vehicle before purchase and it showed no indication of any mechanical issues that I was able to detect. I was shown by the dealership the carfax and was informed that there are currently no recalls for the vehicle. I was led to believe that the vehicle was in good condition and safe to drive and, therefore, agreed to purchase the vehicle for the aforementioned price (including tax and title fees). I purchased the vehicle with 60,077 miles on it, and after driving it normally for only 5 days (on [xxx]) it broke down and I was stranded on the highway 16 hours from home. I was able to get the vehicle towed and paid $1,200 for the starter to be replaced, which is what the mechanic suggested but this ended up being entirely unnecessary as the real issue was due to a catastrophic defect in the engine. After the starter was replaced, I was driving the vehicle only a few days later (on [xxx]) and it suffered a catastrophic engine failure while driving 70mph on the highway. I lost control of the vehicle and nearly got in a collision with another vehicle. I was able to get the vehicle to the nearest auto shop and after inspecting the vehicle they informed me that there is a serious engine issue relating to a seized bearing and the engine will need to be rebuilt entirely. At this point it had been only 12 days since the purchase and the odemeter read 61,662 (1,585 miles driven since purchase). Due to the faulty vehicle, I was forced to pay to have the vehicle shipped from the location where it broke down to the dealership where I originally bought it (around $1,200). Faulkner Chevrolet knowingly sold me an unsafe vehicle that they were well aware had a defective 6.2L V8 engine. This defect is currently under investigation by the NHTSA and faulkner Chevrolet purposefully ommitted this crucial information until after the vehicle was sold. Clearly, this is an unethical bus information redacted pursuant to the freedom of inform

- Schuylkill Haven, PA, USA

I was driving 50mph when my check engine light started flashing. The engine had very little power and there was a new consistent engine knock. I took to GMC dealership and they informed me that half of the engine lifters failed and a pushrod was bent. There was no warning prior to the incident. I have had the vehicle serviced only at the dealership and have only used premium fuel. The truck has 88,000 miles.

- Chesterfield, MI, USA

I've now had 2 engines fail catastrophically, One at 19,191 miles and the second failure at 80,661. Both are the 6.2L engine. The first had crank bearings that were black. The second I was not informed of the cause but that it was seized leaving me stranded on the roadside.

- Holly, MI, USA

Engine failed and had to be replaced. GMC was absolutely no help had to bring to local gas station where i had to pay almost $12,000 to get it fixed. The truck has been in shop frequently for oil issues with this motor but GMC just jerks you around. I am in sales and need my vehicle to support my family

- West Islip, NY, USA

While driving the vehicle shut off in the middle of the roadway. It sat in the road till it got towed. Brought it to the dealership where it was purchased and they said the engine was blown. Themis vehicle is equipped with the 6.2 motor. It happened February 16th. The dealership confirmed the engine failed. It is siting currently at the dealership and could be available for inspection.

- Thorndike, ME, USA

AFM lifters failed which caused cam shaft to collapse under 35k miles. Had to remove while front end to repair

- Plantation, FL, USA

Subject: Complaint Regarding Recurring Engine Failure in 2021 GMC Sierra AT4 Dear National Highway Traffic Safety Administration, I am writing to formally express my concern regarding recurring engine failures in my 2021 GMC Sierra AT4 (6.2L engine). At 23,000 miles, the vehicle suffered a complete breakdown due to failure of cylinder #8, lifters, and push rods. General Motors covered the repairs at that time. However, at 97,000 miles, the exact same issue reoccurred, resulting in significant engine damage. The dealership diagnosed a misfire in cylinder #8, leading to the removal of the right cylinder head, where they found a bent push rod, spun lifter, damaged camshaft lobe, and lifter roller. The repair estimate totals $9,746, but GM has refused to cover the costs, despite us having an extended warranty purchased from the dealership. This recurring failure raises serious concerns about engine reliability and manufacturing defects in General Motors vehicles. I urge the NHTSA to investigate this issue, as multiple GMC and Chevrolet owners have reported similar problems with the 6.2L engine lifter and camshaft system. This is not just a costly repair but a potential safety hazard that GM has failed to properly address. Thank you for your attention to this matter. I appreciate any guidance or action the NHTSA can take to hold GM accountable and ensure consumer protection.

- Pharr (, TX, USA

My Vehicle went into the dealer on January 21, 2025. My initial complaint was tapping noise, I was advised that my vehicle had collapse lifters issue several days later I was informed that they have found metal shards in the lower end and found a bad crank bearing and crank. I was told that the vehicle will need an engine replacement, and that the engine is on back order with no date of fulfilment. My vehicle has 66,700 miles I was advised was out of warranty and that GM will only cover half of the estimated cost of $11,000.

- Voorhees, NJ, USA

The contact owns a 2021 GMC Sierra 1500. The contact stated that while driving at approximately 80 MPH, the vehicle stalled and failed to return to normal operation. No warning light was illuminated. The vehicle was towed to be diagnosed. The contact was informed that the rod bearings needed to be replaced. The vehicle was not repaired. The manufacturer was notified of the failure. The failure mileage was approximately 134,000.

- Springfield, LA, USA

The contact owns a 2021 GMC Sierra 1500. The contact stated while driving 55 MPH, the vehicle started making a knocking sound. There were no warning lights illuminated. The contact picked up his son from school and drove the vehicle to the dealer. The contact stated that while depressing the accelerator pedal, the knocking sound became louder, and the vehicle was losing motive power. The vehicle was taken to a dealer and diagnosed with engine failure. The vehicle was not repaired. The manufacturer was not made aware of the failure. The failure mileage was approximately 58,522.

- Pequot Lakes, MN, USA

While driving on the highway the engine 6.2 GM seized suddenly at high speed. The truck shut off completely and left rolling without any control. I had work my way accross lanes to the breakdown lane. While doing so I was almost hit by an 18 wheel trailer truck, who luckily was able to change lanes to avoid hitting me. The reason I was almost hit was because of my low speed since I had now power or acceleration.

- Bridgewater, MA, USA

I purchased a new 2021 GMC Sierra Denali with a 6.2L engine on 03/05/2022. On November 10, 2022, I started the truck, and the engine seized up. The truck had 9018 miles on it and 274 engine hours. The main bearings and possibly the connecting rods bearings was the problem. On January 27, 2023, I finally got a new engine installed in my truck. I had to pay for the repairs.

- Larwill, IN, USA

Driver side lifters collapsed and push rods failed on freeway without warning at 12900 miles on truck.

- Imperial Beach, CA, USA

On the morning of 1/19/25, my 2021 GMC Sierra 6.2L AT4 went into limp mode heading south on HWY 207 in Leavenworth, WA at approximately 60 m.p.h. Fortunately, I was able to avoid a rear end collision. I quickly turned the truck off in the middle of the road and restarted it with a CEL. When I returned home almost 180 miles away, my local mechanic diagnosed a code P0303 and cleared it. Since, the truck has continued to shutter at various speeds without throwing a code. It is currently at Haselwood GMC in Bremerton, WA being scanned, recorded, and findings set to GM waiting for resolve. I have notes, exact dates, times, call records, return voice mail messages, and dealership personnel spoken to, etc. The dealer-??s lead technician and I were able to replicate the shutter on a road test together on 1/27/25 at 3 p.m. after having driven just 10 miles. During my visit on the morning of 1/30/25, the lead technician stated he has since been able to replicate the shutter seemingly getting worse. I was strongly encouraged by the service manager, service writer, and lead technician their collective -??personal recommendation-?? was to not take the truck back. Haselwood has had the truck since 1/27/25. Still awaiting a response and resolution.

- Seabeck, WA, USA

lifters in the left and right side snapped into 3 pieces. Caused engine failure happened 2 different times. All before 50,000 miles. The first time was before 30,000 miles.

- Alabaster, AL, USA

Engine failure

- Little Silver, NJ, USA

We have had several times where we are on highway and our truck like slams on the brakes causing us to lose control. It was a recall on it and GMC fixed it and within the same week of them fixing it it happened 3 times back to back. Making my truck to force another car to steer out of my way and actually went off the highway. Thank god it was just dirt snd he didn-??t get hurt or anything. But I am scared to even drive my vehicle! It starting Happening for about a year now. And it would only do it like every couple months but now it-??s has done it 6 times in the last 2 months!

- Tehachapi, CA, USA

I was notified at the dealership that my truck had metal in the oil that is causing the oil sensor pump to send a ln engine code. The fix is a new engine.

- Fenton, MI, USA

Engine knocking and metal in oil. Been to the dealership and even though it's under warranty they will not act on it due to no check engine light present. It's making it difficult to trust driving the vehicle anymore because of the thought of the engine shutting down without warning anytime. This complaint is documented and confirmed by a dealership. They made me pay the check out fee and recommended i keep driving the vehicle until the motor locks up.

- Redway, CA, USA