2026 GMC Sierra 1500 engine problems

ENGINE

Vehicle: 2026 GMC Sierra 1500 AT4 (3.0L LZ0 Duramax Diesel) Current Mileage: ~16,500 miles Check Engine Light Status: NO Check Engine Light active Description of Incident & Symptoms: •Interstate Incident: While driving at highway speeds, a severe drivetrain vibration occurred (felt like a rear wheel weight flew off). •Dashboard Warnings: Within 5 minutes, intermittent "Traction Control" and "Forward Collision Warning" alerts appeared on the dash, accompanied by a sudden drop in engine power. •Engine Noise & Idle: Once safely pulled over, the engine exhibited a loud mechanical knock and a very rough, unstable idle. •Extended Crank: After shutting the engine off and waiting a few minutes, restarting the truck took roughly twice as long as normal (long crank/delayed start)

NHTSA complaint #11758123 — an unverified report by a vehicle owner.

ENGINE

Sudden catastrophic engine failure occurred at 7400 miles, 2026 GMC Sierra1500 Denali with 6.2L engine. Driver and 3 children in vehicle headed to school when engine suddenly failed while driving on the roadway. No warning or vehicle symptoms prior. We were told the truck needs a total engine replacement- on a brand new vehicle. It has been nearly 9 weeks with no resolution or repair from GM. The truck was towed to the GM dealership it was purchased from on June 18th and it remains sitting in their service department lot with no timeline for repair or replacement.

NHTSA complaint #11757259 — an unverified report by a vehicle owner.

ENGINE

The contact owns a 2026 GMC Sierra 1500. The contact stated that while driving 70 MPH and depressing the accelerator pedal, the vehicle started decelerating unintendedly. The message “Engine Power Reduced” was displayed. A dealer was contacted. The vehicle was taken to a dealer where it was diagnosed and determined that the engine needed to be replaced. The vehicle was repaired. The manufacturer was notified of the failure and opened a case. The approximate failure mileage was 6,028.

NHTSA complaint #11757030 — an unverified report by a vehicle owner.

ENGINE

The contact owns a 2026 GMC Sierra 1500. The contact stated that while driving 45 MPH and depressing the accelerator pedal, the vehicle slowed down unexpectedly. The vehicle then lost power while stopped at a traffic light. No warning light was illuminated. The vehicle was turned off and restarted, and the vehicle operated as intended. The vehicle was taken to the dealer, where it was diagnosed and determined that there were metal shavings inside the oil pan and the engine needed to be replaced. The engine was replaced twice. The manufacturer was not notified of the failure. The approximate failure mileage was 3,202.

NHTSA complaint #11756457 — an unverified report by a vehicle owner.

ENGINE

Driving on the highway near Rockport, WA, when vehicle suddenly loss propulsion, engine light appeared, and vehicle went into transport mode enabled. Without causing an accident, I was able to pull to the side of the road. Once I put vehicle in park, it shut off and displayed, “Tranport Mode On. Vehicle would not start and was towed home. My son-in-law was able to disable transport mode, but vehicle still will not start. Will notify dealership on Monday.

NHTSA complaint #11755698 — an unverified report by a vehicle owner.

ENGINE

Driving on the highway near Rockport, WA, when vehicle suddenly loss propulsion, engine light appeared, and vehicle went into transport mode enabled. Without causing an accident, I was able to pull to the side of the road. Once I put vehicle in park, it shut off and displayed, “Tranport Mode On. Vehicle would not start and was towed home. My son-in-law was able to disable transport mode, but vehicle still will not start. Will notify dealership on Monday.

NHTSA complaint #11755699 — an unverified report by a vehicle owner.

ENGINE

2026 Denali, 6.2, failed after getting off express way while on my way for a fishing get away and pulling my boat. NO warning lights, noises, nothing. Came to a stop sign and at the last second slammed into park. Dash went black, 10 seconds later would come back on and try to start, then the dash goes black. Sheriff pulled up 20 or so minutes later and told my wife to get back into the vehicle as she was directing semis and other cars to go around. Towed to a chevy dealership 13 miles away. After Running tests on the truck, came up blown engine. 7600 miles. 5 hours later we left with a loaner and able to continue on with our plans. I do thank the dealership for their help and loaner. 23 business days later they delivered my truck to my house and returned in the loaner. After all my investigating on these engines, I will not be buying another one. Time for GM to invest some of their profits into finding the problem!

NHTSA complaint #11755712 — an unverified report by a vehicle owner.

ENGINE

I have a 2026 GMC Sierra 1500 with the 6.2L engine. I purchased it on [XXX]. On [XXX] with 13,000 miles on the truck the engine started making a bad noise from the lower end of the motor. I immediately took it to the dealer Randy Wise Buick GMC in Fenton Michigan. They diagnosed it as a spun bearing and had to replace the engine. I just got it back today August 7th 2026 INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

NHTSA complaint #11755572 — an unverified report by a vehicle owner.

ENGINE

I was driving on 96 W. in slow traffic on the freeway when the vehicle put itself in neutral and shut off

NHTSA complaint #11754782 — an unverified report by a vehicle owner.

ENGINE

Engine died while driving at higher speed on interstate. Barely able to pull to emergency lane before truck stopped. No warning of any issues with it. Had towed to dealership. Dealership confirmed 6.2 engine was faulty. Engine replaced under warranty. Truck only had 1207 miles on it when engine died.

NHTSA complaint #11753938 — an unverified report by a vehicle owner.

ENGINE

While traveling from [XXX] to [XXX] for vacation, I was in [XXX], and when I pulled off the interstate and came to a stop sign the vehicle quit. At first, I was unable to restart the Vehicle, but after sometime I got it started and was able to pull it off the road while the engine was making very loud clattering noise and the vehicle would not stay running. Prior to this there were no warning, lights or indications that the engine was going to quit. I checked the engine oil and it was full. I had the vehicle transported to a GMC dealer in [XXX], where it was diagnosed as requiring a new engine. The vehicle is a 2026 GMC Sierra 1500 Denali purchased in December 2025 and has 8,865 miles on it. A little over 4000 miles I had the vehicle oil changed at Starling GMC Titusville Fl. At the time of my service visit, I asked the service writer, [XXX] to check the engine idle because at times it seemed to run a little rough and it quit while pulling in my driveway one day. [XXX] advised me that there is no idle adjustment on the vehicle, so I said I’ll just keep an eye on it. There were never any indications of an engine problem prior to this or even as of now there are no warnings displayed on the instrument panel. I also subscribe to onstar and it indicates everything in the vehicle is normal with no issues. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

NHTSA complaint #11753455 — an unverified report by a vehicle owner.

ENGINE

6.2 l just blew up per dealership

NHTSA complaint #11753614 — an unverified report by a vehicle owner.

ENGINE

I bought the truck with 2 miles , shut off on me within 1,300 miles wouldn’t turn on , supposedly it was a bad fuse that was burned out , Second time it shut off on me again , all my sensors were going off and on and truck wouldn’t turn back on , they told me they couldn’t figure out the problem evaczue they had disconnected the battery and it erased all the codes 3rd time , they changed my oil and they forgot to torque the screw back correctly and all the oil spilled and cost my engine to lock up and mess up , they replaced the motor with a new one 4th time , supposedly it needs a replacement for a catalytic converter which is being replaced now as we speak or sometime this week

NHTSA complaint #11751712 — an unverified report by a vehicle owner.

ENGINE

While driving vehicle the engine lost power and shut off in traffic. There were no warning signs of issues at that time. The dashboard went blank and then reappeared and the truck was in park. after that the truck would not shift gears. The truck was towed to the dealership and found to have had catastrophic engine failure.

NHTSA complaint #11749941 — an unverified report by a vehicle owner.

ENGINE

Sudden catastrophic engine failure with only 6000 miles on vehicle on May 26, 2026. 2026 GMC Sierra 1500 AT4X with known defective 6.2L L87 V8. Had to coast across three lanes of traffic to get to other median as highway location was on large curve. Someone very easily could have been hurt or killed.

NHTSA complaint #11748047 — an unverified report by a vehicle owner.

ENGINE

My motor has a catastrophic failure. Started sputtering and Squealing.

NHTSA complaint #11746991 — an unverified report by a vehicle owner.

ENGINE

2026 GMC Sierra 1500 AT4X with 3898 miles. Driving 71mph on state highway on flat grade road. Lost power and vehicle shut down after pulling off the road. No previous lights or warning signs prior to power loss. Vehicle would not start afterwards. OnStar Diagnostics sent ECM Engine and Transmission System code P0016. Had vehicle towed 100miles to GM dealership. Upon inspection of vehicle, the Service Department contacted me the following day and said the the vehicle needed an entire engine replacement according to GM cooperate. I asked if it had anything to do with the 6.2L V8 L87 engine problems from previous recall years of 2021-2024. Service tech stated yes it was more than likely the same issue. Very unhappy with my new GM vehicle purchase. Will have to have a full engine replacement BEFORE my first oil change!

NHTSA complaint #11746541 — an unverified report by a vehicle owner.

ENGINE

I was driving on interstate 95 at approximately 70 to 75 mph when I lost all power and compromise steering with tractor trailer behind me God willing I was able to pull over to the shoulder. My safety was compromised and I lost all faith in Gmc. My vehicle has been out of service for 27 days at this point while waiting for an engine replacement with no ETA on service. According to Pennsylvania lemon law after 30 days a lemon law claim can be submitted

NHTSA complaint #11744121 — an unverified report by a vehicle owner.

ENGINE

The contact owns a 2026 GMC Sierra 1500. The contact stated that while driving at an undisclosed speed, there was an abnormally loud and rough knocking sound coming from the engine block. The oil pressure decreased to zero, and the engine seized. There was no warning light illuminated before or after the failure. The vehicle was towed to a dealer, where it was diagnosed with a blown engine. The vehicle was not repaired. The manufacturer was notified of the failure. The failure mileage was 5,018.

NHTSA complaint #11743279 — an unverified report by a vehicle owner.

ENGINE

Total engine failure on 5/31/26. Truck lost engine power while on highway and had to be towed to dealership where they found the lower end of the engine failed. Engine and radiator replacement needed, both are backordered with no eta.

NHTSA complaint #11742302 — an unverified report by a vehicle owner.

ENGINE

I bought a brand new 2026 1500 GMC sierra AT4X and after 1,800 miles the engine seized and failed.

NHTSA complaint #11742370 — an unverified report by a vehicle owner.

ENGINE

While driving approximately 45 MPH, I slowed to make a right turn into a parking lot. The engine suddenly stalled and lost all propulsion. The vehicle retained electrical power but automatically shifted into NEUTRAL, and would not shift back into DRIVE. I braked to a stop, temporarily stranding the vehicle and blocking traffic in the parking area. Attempting to turn the vehicle off via the START/STOP button actually restarted the engine, confirming the stall. The truck then shifted into DRIVE and operated normally. A subsequent OnStar diagnostic scan found no active trouble codes.

NHTSA complaint #11741215 — an unverified report by a vehicle owner.

ENGINE

Heard clanging noise under hood as I was driving and truck just stopped. Tried to restart and nothing! Towed to dealership where they found the engine has to be replaced.

NHTSA complaint #11741251 — an unverified report by a vehicle owner.

ENGINE

While driving on the highway, the steering became much more stiff, and then I heard metallic clanging sounds for a few seconds. The dashboard said press start to start Vehicle. I pressed start while going 30 miles an hour and all lights and instrument clusters went black. I pulled into the grass median where the truck would not start or shift gears. Truck was towed to a GMC dealership

NHTSA complaint #11740289 — an unverified report by a vehicle owner.

ENGINE

The contact owns a 2026 GMC SIERRA 1500. The contact stated while driving 40 MPH, the vehicle independently engaged into limp mode. A dealer was contacted. The vehicle was towed to the dealer where it was diagnosed that the engine needed to be replaced. The vehicle was not repaired. The manufacturer was not notified on the failure. The approximate failure mileage was 10,000.

NHTSA complaint #11739028 — an unverified report by a vehicle owner.

ENGINE

On or about 12/14/25 at approximately 2,000 miles my engine began smoking to the point that it was pushing in to the interior of the cabin and created a cloud like atmosphere that smelled of burning oil. There were no warning messages in the vehicle or in the mobile diagnostic application associated with the vehicle. Once parked, I popped the engine and observed visible smoke from the engine and a distinct crackling noise coming from the area of the engine. I checked underneath the vehicle and was able to see oil dripping and, subsequently, feel oil running down a majority of the undercarriage of the truck. Ultimately, I had the vehicle towed the dealership and they diagnosed a front cover seal for the engine was leaking and repaired the issue. On 3/20/26 I had to take my vehicle in for an early oil change due to the above issue and low oil life. Since the above repair, I had continued to smell intermittent burning oil in the cabin of the truck. During the oil change I asked the GM service provider to check to ensure the same issue had not recurred and, following the oil change, I was informed they did not see any issue. On 5/8/26, at approximately 7,000 miles, the same issue regarding visible smoke in the cabin occurred and, upon opening the hood, I was able to see visible smoke from the engine and hear the same crackling noise. I checked underneath the vehicle and, again, was able to see oil dripping and feel it on a majority of the underside of the truck. There were no warnings, in the vehicle or in the GM app for the vehicle, associated with the failure. Again, I took the vehicle to the GM dealer service center. The diagnosis was a leaking rear cover seal. Upon repairing this issue, GM service discovered "flakes" in the oil in the engine and diagnoses a failing thrust bearing that indicated engine failure. I have documentation of the diagnosis and attempted repairs but, am not currently in a location that I can scan and upload them. I can provide them.

NHTSA complaint #11737424 — an unverified report by a vehicle owner.

ENGINE

The engine started having knocking and I took it to the dealership and now I have been waiting 45 days with no engine replacement in site after they told me the engine failed completely. It had 3,900 miles on the engine!

NHTSA complaint #11736788 — an unverified report by a vehicle owner.

ENGINE

6.2 ENGINE BLEW UP 3000 MILES

NHTSA complaint #11735797 — an unverified report by a vehicle owner.

ENGINE

I bought the truck brand new from Gregg Young in Atlantic, IA. While an hour into the drive home, the truck began shuttering as if the transmission was having problems finding the gear. I immediately made an appt with their parent dealership of Gregg Young in Plattsmouth, NE. They had the truck for a week and couldn’t duplicate the transmission issues after I reported several occurrences and symptoms, they also didn’t provide a service invoice of the work performed while I found was unusual. As I was driving the truck home from repairs it started hesitating and having difficulty finding gears. I didn’t think much of it since the dealer claimed there was nothing wrong. This past weekend while going 65 mph down the freeway the transmission started shuttering as well as the truck and the tires began to lock up to the point of almost losing control, there was also metal on metal noises. I had to pull over and luckily driving real slow I made it home. The Gregg Young dealership were I bought it will take no responsibility and provided falsification since no service was provided nor upon checking app gps there was no indications it left the dealership while in there possession for a week, will contact GMC in the AM since this has now become a safety issue and there was metal on metal contact noises and the serious risk of a crash.

NHTSA complaint #11732292 — an unverified report by a vehicle owner.

ENGINE

ENGINE LOCK UP WITH 5018 MILES ON, IT IS A THE 6.2 MOTOR ROD AND CRANK BAD

NHTSA complaint #11730419 — an unverified report by a vehicle owner.