2026 GMC Sierra 1500 Problems

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!

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.

The contact owns a 2026 GMC Sierra 1500. The contact stated that while her husband was driving approximately 10 MPH, the vehicle unexpectedly shut off and independently shifted into park(P). The contact stated that previously, while the vehicle was idling in a parking lot, with air conditioner activated, the Auto START/STOP feature engaged, and the vehicle shut off. The message “Service Transmission” was displayed. The vehicle was taken to a local dealer and was diagnosed with transmission failure. The vehicle was not repaired. The manufacturer was not contacted. The failure mileage was approximately 2,000.

I am submitting this complaint to report what I believe is a serious safety-related defect involving the General Motors 6.2L L87 V8 engine installed in my 2026 GMC Sierra Denali. On July 10, 2026, while driving on a public highway near Bogata, Texas, the engine suddenly began making severe mechanical noises before catastrophically failing without warning. The engine seized completely while the vehicle was in motion. At the time of failure, the truck had only 13,517 miles. The sudden loss of engine power left my wife and me stranded on the roadside. Had this occurred while crossing an intersection, merging into traffic, passing another vehicle, towing a trailer, or traveling in heavier traffic, the consequences could have been far more serious.

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.

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.

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

The telematics module for the OnStar system continues to stop working, I have had this truck in a dealership service center multiple times for them to reset the system (instead of replacing the defective parts). Along with the infotainment system not working properly (cuts in and out, blinks on/off, delay in actions) Doors unlock while driving, front/rear cameras come on when I stopping at an intersection, I have given them documentation of the diagnostic reports from dealerships

In early June 2026 I discovered a sheared pin on the front control arm of my 2026 GMC Sierra 1500 AT4X (VIN [XXX]), sold to me new by Parks GMC, Kernersville NC, with a dealer-installed Performance Package modifying the factory suspension. I delivered the truck to Parks GMC for warranty repair. The dealer represented it as a 1-2 day job. The truck was out of service approximately 2 weeks. The dealer sub-contracted the work to a third-party shop (CCV). At pickup, the dealer provided written documentation stating the repair was NOT PERFORMED. Neither the dealer nor I has been able to obtain any documentation from CCV describing what, if anything, was actually done to the vehicle. THREE UNRESOLVED SAFETY CONDITIONS: SHEARED FRONT CONTROL ARM PIN — original failure, status of repair unknown and undocumented. TIRE-TO-BODYWORK CONTACT — front tires intermittently rub the inside of the wheel wells during normal driving and steering, causing visible damage to the plastic mud guards. Tire-to-bodywork contact creates risk of sidewall failure, sudden air loss, and loss of vehicle control. FRONT RIGHT SUSPENSION CREAK — loud, persistent creak from the front right suspension during low-speed driving and steering inputs. Present at service drop-off, never addressed. Consistent with a worn, loose, or improperly installed suspension component. I escalated to Parks GMC management and GMC Customer Assistance. Parks has not provided a written repair plan, no decision-maker has contacted me, and the only response has been "looking into it." GMC Customer Assistance declined to assign a District Service Manager. I am filing to document these suspension and tire safety conditions in the federal database against this VIN and to request NHTSA evaluation of whether further action is warranted. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

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

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

"Vehicle is experiencing symptoms consistent with the 6.2L L87 engine bearing failure investigation (NHTSA Probe January 2026). Despite two repair attempts, the dealer claims 'operating as designed.' I have experienced persistent engine stumble,hesitation, erratic tachometer needle flutter and significant vibrations felt through the floorboard and seats during operation. These defects substantially impair the use ,value and safety of my vehicle.This is a serious safety concern as it creates a risk of catastrophic engine seizure at highway speeds. Manufacturer has been sent a formal 'Last Chance' letter under NJ Lemon Law." Reference # 1771884

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.

I was out one day for lunch and my brakes stopped working on my truck. I had the truck towed after I limped home in it. The master cylinder failed at 4,200 miles causing the brakes to fail. It was replaced by the dealership.

My 2026 GMC Sierra has an oil-canned roof from a touchless car wash because the sheet metal lacks structural rigidity. This caused the roof to buckle and caused a permanent fold in the roof of the truck. There is already documented issues for this exact problem on the newer GMC Canyons and Chevrolet Colorado mid-sized trucks. Bulletin for reference NHTSA Official TSB #23-NA-209 PDF. I leased the vehicle on 6/19/2026 and this happened on approximately 7/7/2026. The vehicle only has 1,480 miles on it as of this date.

The tailgate intermittently opens while driving or parked

In early June 2026 I discovered a sheared pin on the front control arm of my 2026 GMC Sierra 1500 AT4X (VIN [XXX]), sold to me new by Parks GMC, Kernersville NC, with a dealer-installed Performance Package modifying the factory suspension. I delivered the truck to Parks GMC for warranty repair. The dealer represented it as a 1-2 day job. The truck was out of service approximately 2 weeks. The dealer sub-contracted the work to a third-party shop (CCV). At pickup, the dealer provided written documentation stating the repair was NOT PERFORMED. Neither the dealer nor I has been able to obtain any documentation from CCV describing what, if anything, was actually done to the vehicle. THREE UNRESOLVED SAFETY CONDITIONS: SHEARED FRONT CONTROL ARM PIN — original failure, status of repair unknown and undocumented. TIRE-TO-BODYWORK CONTACT — front tires intermittently rub the inside of the wheel wells during normal driving and steering, causing visible damage to the plastic mud guards. Tire-to-bodywork contact creates risk of sidewall failure, sudden air loss, and loss of vehicle control. FRONT RIGHT SUSPENSION CREAK — loud, persistent creak from the front right suspension during low-speed driving and steering inputs. Present at service drop-off, never addressed. Consistent with a worn, loose, or improperly installed suspension component. I escalated to Parks GMC management and GMC Customer Assistance. Parks has not provided a written repair plan, no decision-maker has contacted me, and the only response has been "looking into it." GMC Customer Assistance declined to assign a District Service Manager. I am filing to document these suspension and tire safety conditions in the federal database against this VIN and to request NHTSA evaluation of whether further action is warranted. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

The contact owns a 2026 GMC Sierra 1500. The contact stated that after purchasing the vehicle, there was no Owner’s Manual in the vehicle. The contact inquired about the Owner’s Manual and was informed by the dealer that an Owner’s Manual was no longer printed. The contact checked online and became aware of FMVSS 225, which was related to the Owner’s Manuals for similar vehicles. The contact researched NHTSA Campaign Number: 25V815000 (Equipment), addressing the lack of an Owner’s Manual for 2026 Chevrolet Silverado 1500, 2500, and 3500 vehicles. The manufacturer was not notified of the issue.

In early June 2026 I discovered a sheared pin on the front control arm of my 2026 GMC Sierra 1500 AT4X (VIN [XXX]), sold to me new by Parks GMC, Kernersville NC, with a dealer-installed Performance Package modifying the factory suspension. I delivered the truck to Parks GMC for warranty repair. The dealer represented it as a 1-2 day job. The truck was out of service approximately 2 weeks. The dealer sub-contracted the work to a third-party shop (CCV). At pickup, the dealer provided written documentation stating the repair was NOT PERFORMED. Neither the dealer nor I has been able to obtain any documentation from CCV describing what, if anything, was actually done to the vehicle. THREE UNRESOLVED SAFETY CONDITIONS: SHEARED FRONT CONTROL ARM PIN — original failure, status of repair unknown and undocumented. TIRE-TO-BODYWORK CONTACT — front tires intermittently rub the inside of the wheel wells during normal driving and steering, causing visible damage to the plastic mud guards. Tire-to-bodywork contact creates risk of sidewall failure, sudden air loss, and loss of vehicle control. FRONT RIGHT SUSPENSION CREAK — loud, persistent creak from the front right suspension during low-speed driving and steering inputs. Present at service drop-off, never addressed. Consistent with a worn, loose, or improperly installed suspension component. I escalated to Parks GMC management and GMC Customer Assistance. Parks has not provided a written repair plan, no decision-maker has contacted me, and the only response has been "looking into it." GMC Customer Assistance declined to assign a District Service Manager. I am filing to document these suspension and tire safety conditions in the federal database against this VIN and to request NHTSA evaluation of whether further action is warranted. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Ac not working properly. Ac blows air to defrost vents foging front windshield and side windows causing bad visibility