2024 GMC Sierra 1500

As I was driving down the road, I heard a loud explosion. I looked around, didn't see anything that could've hit the truck. I thought it was possibly a gunshot that went off. After driving for another 3 or 4 minutes, I heard glass going everywhere. It was the moonroof that exploded. Thankfully, the sunroof cover was in the closed position. Otherwise, glass would've been all over the interior of the vehicle. I called the dealership to report the incident and to see if this was something that could be covered under warranty. I'm still waiting for a call back. I then called my insurance company to report what happened. I was told to seek a repair shop and collect all receipts for the claim. No warning lights have appeared in the vehicle yet. Since we were driving home from a vacation, we stopped and got a roll of vinyl sticker to cover the outside from rain.

Lifters and camshaft failure, loud clanking, & sudden power loss on the 6.2 motor are the first noticeable signs. Instantly when everything happened check engine light, cruise control, & stabilizer lights flashed. The sudden loss of power forced the vehicle to suddenly slow down forcing my camper into the truck. I was hauling a within weight standerd camper but had difficulty bringing both the truck with the camper to a safe stop. There were no early signs or signal prior to sudden cautostrophic engine failure & all service records have been completed by a GM certified service dealer.

While driving on a divided two lane state highway at approximately 60mph my vehicle suffered a catastrophic engine failure causing immediate loss of power in traffic at highway speeds. I had to negotiate highway traffic to steer the vehicle onto a narrow shoulder and continue under reduced power to a location where the vehicle could remain stopped safely. There were no warning signs and no warning lights prior to the issue. The vehicle was towed to Faulkner GMC where it was eventually inspected and determined to be an engine failure consistent with the open recall affecting GM 6.2 L87 V8 engines. A replacement engine was installed under warranty. Additionally, a defective tailgate switch was discovered and replaced. A prior unrelated incident had occurred where the tailgate switch activated on its own lowering my tailgate while the vehicle was in motion. The tailgate lowered onto the tongue jack of a trailer I was towing causing damage to the tailgate. This issue occurred multiple times throughout my ownership of the vehicle until the switch was replaced. GM acknowledged the switch was found to be defective but refused to take responsibility for the damage.

My vehicle has experienced repeated and unresolved electrical system failures and unexpected loss of power steering assist. The problem involves multiple warning lights, module communication faults, drivability issues, and simultaneous malfunctions affecting systems including power steering, traction control, transmission, four-wheel drive, and other electronic controls. Repair records, diagnostic information, and videos documenting the failures are available for inspection upon request. The most serious incident occurred on August 23, 2026, when the power steering failed unexpectedly while I was driving. The sudden loss of steering assist made the vehicle difficult to control and nearly resulted in a collision with an oncoming vehicle. The failure created a significant safety risk because it impaired my ability to safely steer and control the vehicle. The condition has occurred multiple times over several months and has resulted in repeated dealership visits. Repairs have included replacement an HVAC controller, but the failures have continued. The vehicle has been inspected multiple times by an authorized dealer, and the manufacturer has been notified through an open support case. As of the most recent repair visit, no confirmed root cause or permanent repair had been identified, and the dealership was still working with engineering support to diagnose the issue. Prior to and during these failures, numerous warning lamps and service messages appeared, including warnings related to power steering, traction control, transmission, four-wheel drive, trailer brake system, steering column lock, and tire monitoring systems. In some incidents, the vehicle entered reduced-performance mode. These warning messages first appeared in November 2025 and have continued intermittently despite multiple repair attempts. The recurring and unresolved loss of power steering assist while driving creates an ongoing risk of crash or injury.

I purchased a 2024 GMC Sierra 1500 Denali Ultimate equipped with the 6.2L V8 engine on XXX. The vehicle currently has approximately 25,000 miles. On XXX, the vehicle underwent the GM recall repair related to the 6.2L engine at Don Mealey Chevrolet. On XXX, approximately nine months after the recall repair, my family and I were traveling on the [XXX] with my two children inside the vehicle when the engine suddenly experienced a major failure. The vehicle became inoperable while we were traveling on the highway and had to be stopped and subsequently transported to Schumacher Buick GMC in [XXX]. The failure occurred unexpectedly while the vehicle was being operated normally. Having an engine failure while traveling on a major highway with my two children in the vehicle created a significant safety concern because of the potential for loss of power and the danger associated with becoming disabled in active highway traffic. GM has subsequently authorized replacement of the engine under warranty. The vehicle remains at the dealership awaiting completion of the engine replacement. I am reporting this failure because the vehicle had previously received the GM recall remedy for the 6.2L engine issue and subsequently experienced a major engine failure at only approximately 25,000 miles. The failure occurred approximately nine months after the recall repair. I am concerned that the previous recall remedy may not have adequately addressed the underlying condition associated with these 6.2L L87 engines. I am requesting that NHTSA document this failure as part of its investigation into 6.2L L87 engine failures and evaluate whether the existing recall remedy adequately addresses the safety-related engine failure condition. Vehicle information: * [XXX] GMC [XXX] 1500 Denali Ultimate * 6.2L V8 engine INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

The vehicle was part of the GM L87 engine recall. The vehicle was taken to the dealership in late 2025 for recall service. The dealership inspected the vehicle for vibration and determined that it required an oil change and updated service manual to require 0W-40 oil. On June 21, 2026 the vehicle experienced an engine failure.

After the initial recall inspection was performed, I was informed that my vehicle was not affected. Subsequently, the vehicle experienced a catastrophic engine failure while traveling westbound on [XXX] near [XXX], approximately one mile from [XXX]. While traveling at highway speed, the vehicle suddenly began losing speed and power. I was positioned between two semi-trucks, creating an extremely dangerous situation. At first, I looked to see if I was traveling uphill because of the unexpected loss of speed. I then pressed the accelerator in an attempt to maintain highway speed. The vehicle abruptly downshifted and the engine RPM increased dramatically. Immediately afterward, warnings appeared on the instrument cluster, including “Engine Oil Temperature High” and instructions to pull over and allow the vehicle to cool down. The vehicle continued to lose power, creating a serious risk of collision due to the surrounding highway traffic. The vehicle was subsequently towed to Findlay GMC, where it was inspected and diagnosed with a failed engine. The engine was ultimately replaced. This failure occurred after the vehicle had been inspected under the recall and I had been advised that it was not affected. I am concerned that my vehicle may have been incorrectly excluded from the recall or that the recall does not adequately identify all affected vehicles. The sudden loss of propulsion at highway speed presented a significant safety risk and warrants further investigation. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)