2026 GMC Sierra 1500 Driver assistance Problems

6 month old, 9,000 miles 2026 Sierra 1500 with Duramax 3 liter suffered an engine control module failure 4 hours into a 12.5 hour drive home from family vacation. First a transmission service warning flashed, then an emissions system failure with a forced speed reduction warning. This happened with two children and a dog in the vehicle. OnStar did diagnotics and said I had to see a dealer. Fortunately one was nearby and they determined the engine control module needed to be replaced--but i was 8.5 hours' drive from home with kids and dog and would have had to stay for 2-4 days awaiting parts and repair. I traded the truck at the dealer for a new vehicle and drove that home. This was a major safety concern traveling with children and a dog on a nearly 100 degree day. And it was a brand new vehicle.

NHTSA ID

11752717

Incident

Jul 22, 2026

I purchased this new full-size heavy-duty pickup, and at purchase the selling dealer installed a 3-inch suspension lift kit with 37-inch tires on 22-inch wheels as a paid dealer upfit. The lift kit manufacturer publishes a maximum tire size of 35 inches on a 20-inch wheel for this kit; the tires and wheels the dealer installed exceed that spec. The lift manufacturer confirmed directly that they would never approve exceeding the 35-inch tire / 20-inch wheel recommendation. The dealer's assistant manager confirmed that NO calibrations of any kind were performed after the lift and 37-inch tires were installed, and said nothing is recalibrated when a lift is done with 37-inch tires. This vehicle is factory-equipped with forward collision alert, automatic emergency braking, front pedestrian braking, lane departure warning, and automatic high-beam control. These crash-avoidance systems rely on forward-facing camera and sensor aim, which depends on ride height and suspension geometry. A 3-inch lift with 37-inch tires materially changes that geometry. With no calibration performed, there is no assurance these safety systems are aimed or functioning to spec. The truck was also never aligned after the lift and the tires are cupping. The headlights were never re-aimed for the higher ride height, and the speedometer was never recalibrated and reads inaccurately. The oversized tires also contact the body. The left front tire has torn into the front fender, the fender well is misaligned, and it is forcing the lower front edge of the driver's door out of alignment. The dealer's only proposed remedy is to keep cutting the fender wells; the trimming already done has exposed electrical wiring behind the wheel well to mud, water, and road debris. I am reporting this because the assistant manager's statement suggests it may be the dealer's standing practice—other customers may be driving lifted trucks with uncalibrated crash-avoidance systems without knowing it.

NHTSA ID

11750542

Incident

Jun 23, 2026

No sound at different times. No way to reset issue. TSB issued May 14, 2026 for known issue. As of July 6, no estimate on repair. Blinkers make no sounds, Onstar can call but you cannot hear them. In event of accident, no communication.

NHTSA ID

11748779

Incident

Jul 1, 2026

I bought my 2026 GMC in April. Several times the audio doesn't work work. When this happens audio related safety technology is affected too including turn signal sounds and back camera audio also. A person walking behind the truck can be seen on the screen but no warning beeps are heard. When backing up the warning for getting too close to an object also doesn't work. I called the dealer in early May and was told that this was a known issue and that it needed a software update. took the truck to the dealer on May 8th and the software update was performed. When the update had been completed when I started the truck after the update there was no audio. I told the service advisor it was currently happening and she took it back to the technician. They disconnected the battery cables to reset the system and told me to do that in the future until the issue is resolved. I opened Case #100978480 with GM on June 1st because I wanted to be sure that GM was also informed of the issue. I was hoping they would be proactive and report back to me what they were doing to resolve this issue. Instead I was told that I need to call the dealer and the dealer would call GM because an update might be available but dealers wouldn't be informed and wouldn't check unless I called.

NHTSA ID

11747094

Incident

Jun 28, 2026

Traveling home the day I purchased vehicle going through [XXX] with cruise set on 35,negotiating a right handed curve in the road and a vehicle was stopped in center lane turning left and my vehicle abruptly braked causing the vehicles behind me to take evasive action to keep from hitting me from behind INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

NHTSA ID

11740285

Incident

May 23, 2026

Vehicle keeps displaying a warning message to service drivers assistance system. Taken the vehicle to the dealership multiple time and the condition still persists. Dealership contacts GM tech support and are being told that GM is aware of the problem, programing issue, but they have no solution after several months. Multiple vehicles at many dealerships have the same problem. I don't feel safe driving the vehicle. Drivers assistance system includes multiple cameras and sensors. This condition could cause severe accidents of even death if the system gives false or wrong information

NHTSA ID

11731366

Incident

Dec 31, 2025

While driving at approximately 60 mph on an open road with no obstacles present and no braking input, the rear wheels spontaneously locked up without warning. No brake pedal input. No warning light prior to the event. No obstruction in the road. The vehicle has been subject to an active manufacturer recall for rear wheel lockup due to transmission control valve failure. The dealer's own diagnostic system generated a report showing six active fault codes in the following days including lost communication with the Brake System Control Module and Transmission Control Module. These codes were not addressed on the repair order. The dealer attributed the lockup to an Automatic Emergency Braking activation without diagnostic confirmation and performed no repair. The manufacturer's own internal bulletin dated January 22, 2026 acknowledges the exact fault codes present on this vehicle as a known defect. The dealer cited this bulletin to dismiss the concern while stating no problems exist. A persistent brake noise has been confirmed by two separate authorized dealers across three visits with no repair performed at any visit. The vehicle has required five dealer visits in 77 days of ownership with 1,729 miles. The defect remains unresolved and poses serious risk of loss of vehicle control at highway speed.

NHTSA ID

11726026

Incident

Mar 15, 2026

I am the owner of a 2026 GMC Sierra 1500 Denali Ultimate equipped with the 6.2L V8 L87 engine (VIN: [XXX] ), purchased new approximately three months ago. I am filing this complaint proactively. I have experienced no engine failure or symptoms to date. However, I am filing based on a documented pattern of L87 engine failures in 2025 and 2026 production vehicles, confirmed by multiple GM dealership technicians, which suggests that the manufacturing defect underlying NHTSA Recall 25V-274 may not have been fully resolved by GM’s stated production improvements dated June 1, 2024. NHTSA Recall 25V-274 (April 2025) covered 597,630 vehicles from model years 2021–2024 for catastrophic L87 engine seizure caused by connecting rod bearing failure and crankshaft defects. GM excluded 2025 and 2026 model year vehicles based on a claimed manufacturing fix. However, multiple 2026 production vehicles have since experienced the same bearing failure at extremely low mileage. Open NHTSA Investigation EA25007 is already examining vehicles outside the original recall window, and Recall Query RQ26001 is investigating the adequacy of GM’s remedy. I am requesting that NHTSA consider expanding the investigation scope to include 2025 and 2026 model year vehicles. As a 2026 owner of a $90,000+ truck with the identical engine configuration, I believe my vehicle warrants inclusion in any expanded investigation or recall action. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

NHTSA ID

11724264

Incident

Mar 14, 2026

My engine seized up on me on the highway. I was stranded and couldn’t start the vehicle and it was freezing outside.

NHTSA ID

11721299

Incident

Feb 23, 2026

GMC SUPER CRUISE MALFUNCTION NO WARNING BEFORE SUPERCRUISE SHUTS OFF PASSING A CAR ON FOUR LANE HIGHWAY (SUPER CRUISE ENABLED) SUPER CRUISE SHUT OFF AND TRUCK CONTINUED HEADING FOR THE CENTER GAURD RAIL.(I CAUGHT IT BEFORE IT BECAME AN INCIDENT). SUPER CRUISE ABRUPTLY SHUTS OFF (NO WARNING) AND WITHIN A COUPLE THOUSAND FEET IT TURNS ON. MY FIRST TIME USING SUPERCRUISE AZ HIGHWAY 87 N BOUND JUST BEFORE RYE AND AZ HIGHWAY 260 BETWEEN PAYSON AND CHRISTOPHER CREEK I CALLED MY DEALERSHIP BUT IT WAS LIKE UH HUH OK I'LL LET GM KNOW.- NO SUPPORT! THE ONLY INDICATOR IS ON THE STEERING WHEEL A RED,GREEN OR YELLOW LIGHT.RED IS OFF-GREEN IS ACTIVE, AND YELLOW LIGHT NO SERVICE. RED LIGHT COMES ON AND SEAT VIBRATES SUPERCRUISE DROPS OUT.

NHTSA ID

11712904

Incident

Jan 9, 2026