2026 GMC SIERRA 1500 Complaints

Truck milage at the time of engine failure was 9,101. Well past the break in period for towing. We were towing a car trailer 2,000 pounds less the max towing capacity for the truck and going less than the posted speed limit. The truck was also in tow haul mode. The truck dash flashed oiled heating hot. We tried to pull over on the highway then the truck lost all power and overheated. Our trailer was not all the way off the highway, so a WY State Trooper pulled behind us and kept his lights flashing for 3 hours until a tow truck came. Truck could not be placed in neutral, so it had to be dragged onto the flat bed ramp of the tow truck. Truck was towed to the Gillette WY GMC dealership that same day. On Monday we were informed that the engine failed and needed to be totally replaced. The GM dealer cannot tell us how long it will take to get the new engine or how long we will be without the truck. This is the 6.2 V8 which GM assured buyer's of 2026 vehicles that the engine failures reported on previous year vehicles had been rectified on the new models. Less than 10,000 and the engine failed.

What component or system failed or malfunctioned, and is it available for inspection upon request? The truck has lost power unexpectedly while driving, and lately I've also noticed some lag when I accelerate. The truck is available to be inspected. How was your safety or the safety of others put at risk? The truck suddenly lost power while I was driving and told me to restart the vehicle. Losing power unexpectedly almost caused me to get stuck in an intersection and could have caused an accident in a busy shopping center. Has the problem been reproduced or confirmed by a dealer or independent service center? No. I took it to the GMC dealership after the second time it happened, but they couldn't get it to do it again and said there were no codes showing. They told me to bring it back if it happens a third time. Has the vehicle or component been inspected by the manufacturer, police, insurance representatives or others? Yes. I took it to the GMC dealership to have it checked after the second power-loss issue happened. Were there any warning lamps, messages or other symptoms of the problem prior to the failure, and when did they first appear? When it lost power, the truck prompted me to restart the vehicle. I have also recently started noticing some lag when accelerating and starting the vehicle. There was no warning before it happened.

I bought the vehicle brand new in april 2026. On May 3rd, approximately 2 weeks after I bought it, I experienced a lifter failure that caused metal to get into the oil pan/engine and the engine needed to be replaced. About a month later after repairs were complete, I picked up my vehicle on a Friday night, and the very next morning, had issues again. Took it back to the dealer and a fuel injector went bad and needed to be replaced. I recently attempted to use the remote start feature and as soon as it fired up, the engine cut out. I went to start it again and the check engine light came on. My GMC app said the code was transmission related, although it cleared on its on the next morning after a software update.

Bought the vehicle brand new at the end of april. 2 weeks later and at 557 miles, the engine had a lifter failure and needed to be replaced. One day after picking it up after the engine replacement, a fuel injector went bad and needed to be replaced. About 2 days ago, the check engine light lit up, and the GMC app said it was a code for the transmission system (popped on after attempting to remote start the vehicle, although the light did shut off on its own the next day after a software update on the vehicle)

The contact owns a 2026 GMC Sierra 1500. The contact stated that intermittently there was no sound while the turn signals were activated, and the radio and incoming calls failed to be audible. The issue often lasted all day or for an hour or two before returning to normal. The contact associated the failure GM Technical Service Bulletin: PIT6406 (or PIT6406F), but the dealer stated the vehicle was not included in the bulletin and refused further diagnostic tests. The vehicle was taken to a dealer to reprogram the Audio Control Module (ACM) because the software was outdated, despite the vehicle being brand new. The reprogramming was completed; however, the failure was not resolved. The manufacturer was notified of the issue. The failure mileage was 3,657.

This engine has used more than 2 quarts of oil since purchased in November of 2025. It has 12,000 miles on it. The exhaust pipes are covered in black soot from oil burn. It scares me to drive it, $87,000 retail vehicle worth about nothing with a bad engine. Terrible

I bought a new GMC Sierra 1500 Denali with the 6.2L V8 engine in December of 2025. 7 months later, I was driving home from work. When the car started, it sounded a little louder, but not out of the ordinary. I started driving and got a strange rattle when I was getting on the highway at around 65MPH. I pulled off at the next exit and checked my fluids, checked under the car to see if anything was caught that was causing the rattle. All pressures and fluids were normal. I had Onstar run a system diagnostic. The diagnostic read normal. I got back on the highway and drove about 20 miles at 75mph. The rattling continued. 20 miles later, the check engine light came on. I had onstar run a diagnostic and came back stating “engine and transmission system problem” with two error codes. One code said “An issue has been detected in the Variable Valve Timing System adjust the timing of fuel delivery for more efficient engine operation”. The other code said “An issue has been detected in the Ignition System which oversees the timing and spark necessary to ignite fuel in your engine” Both error codes said to fix within one day. The GMC dealership was on the way home so I was going to stop there and see what they could do. I never made it to the dealer. About 2 minutes after the diagnostic, while doing 75mph on the highway, I hit the accelerator and the car did not speed up. The engine then shut off while I was in the left lane doing 75 mph. The electronics stayed on and the dash stated “press start to start engine.” I pulled over to the side of the highway and put the car in park and attempted to restart the engine. The engine never turned over again. I could not get the engine to start. I could not shift the car to neutral to have it rolled up on to the tow truck. My truck was towed to the GMC dealership and they are now replacing the engine under warranty. Will upload any maintenance paperwork once engine is replaced.

I purchased this new 2026 GMC Sierra 1500 on 07/16/2026. Beginning shortly after delivery, the vehicle began intermittently losing ALL audio, including the audible turn-signal indication. The condition now occurs approximately once every 3–4 vehicle starts/uses. When the failure occurs, there is no audio from the infotainment system, radio, Apple CarPlay, Bluetooth, or speakers, and there is no audible turn-signal sound. Because the failure also eliminates audible driver feedback from the turn signals, I am concerned this is not simply an entertainment-system issue. The vehicle is available for inspection upon request. The vehicle was presented to Ed Morse Sawgrass Auto Mall, an authorized GMC dealer, after the condition occurred again on approximately 08/20/2026. The dealer advised me that the vehicle already has the applicable software programming and that GM is aware of the condition. The Service Manager advised me in writing that GM currently instructs the dealer to recover/reset the radio and not replace the radio or amplifier because GM is working on a permanent correction. Restarting the infotainment system, Safe Mode, disabling Quick Startup, and allowing the vehicle to completely power down have not permanently corrected the condition. A full shutdown may temporarily restore the audio, but the failure returns. There are no warning lamps or messages before the failure. The audio simply does not function when the vehicle is started. The vehicle currently has approximately 976 miles. There has been no crash, fire, injury, or fatality. I have also formally reported the condition to GMC Customer Assistance. GMC Case #108458085.

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)

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.