2024 GMC Sierra 3500

"The integrated trailer brake system abruptly fails while towing heavy loads, completely disabling trailer break stopping power and creating an imminent threat of highway crash and serious bodily injury." The sound system inherently stops working and will not produce sound from any device in the truck weather that be Hazards, Blinkers, Radio including AM,FM, Sirus Radio, Bluetooth or Car play as well as OnStar. The truck has been taken to a certified GMC dealer 4 times for these exact issues with also being provided the service bulletin information #N232414840 dated July 16, 2025 stating that the 2024 gmc 2500/3500 HD trucks requiring a new Trailer Break Control Module. This issue has been on going from September 2025 and still an issue as July 16, 2026 and still in the Shop today with a call back stating ready for pick up with the same module but dealer stated re flashed module. ( this is the 3rd reflash )

This 2024 GMC Sierra Heavy Duty has experienced a continuous pattern of major mechanical and electrical failures since early ownership. The vehicle required a complete engine replacement under warranty at approximately 43,626 miles. Since that time, the vehicle has continued to experience repeated injector failures, control module faults, communication errors, and voltage-related system issues. Current diagnostic codes indicate multiple simultaneous failures including ignition relay feedback circuits, control module power faults, gateway communication loss, brake system communication faults, and battery voltage circuit errors. The dealership has diagnosed a power distribution / fuse block failure at approximately 79,000 miles. These electrical failures affect multiple vehicle systems and raise concerns regarding reliability and potential safety risks due to loss of communication between control modules and possible braking system interaction. The vehicle has been in the dealership numerous times for repairs including engine replacement, injector replacement, control module reprogramming, and electrical diagnostics. I am submitting this complaint due to concern over a potential systemic electrical defect and ongoing reliability issues.

The contact owns a 2024 GMC Sierra 3500. The contact stated while driving at approximately 60 MPH and towing a Forest River Riverstone Legacy 5th Wheel trailer, the brake pedal was depressed to slow for oncoming stopped traffic; however, the vehicle failed to respond as needed with the “Service Trailer Brake” warning light illuminated. The contact was able to stop however, the brake pedal had to be depressed to the floorboard to slow the vehicle. The contact had taken the vehicle to a local dealer and was made aware of Customer Satisfaction Program: N232414840 - and replaced the Trailer Brake Power Module (TBPM). The vehicle was repaired; however, the failure reoccurred. The contact returned the vehicle to the same dealer and the Trailer Brake Power Module was replaced a second time. The vehicle was repaired; however, the failure reoccurred. The contact had taken the vehicle to another dealer who diagnosed the vehicle and determined that the failure was with the 5th Wheel RV. The vehicle was not repaired. The manufacturer was informed of the failure. The failure mileage was approximately 20,000.

The contact owns a 2024 GMC Sierra 3500. The contact stated that the exterior lights of the vehicle were flashing erratically, and the tailgate was opening unintendedly. The contact stated that while driving at various speeds, the vehicle experienced erratic transmission shifts, and the vehicle was jerking and made an abnormal clunking sound. The check engine warning light was illuminated. The contact pulled over to a truck stop and parked the vehicle. The contact stated that the battery became fully drained while parked with the windows rolled down in snowy weather. The contact stated that after waiting 6 hours for AAA to arrive, the vehicle jump-started. The contact stated that the battery had drained on several occasions. The vehicle was taken to the dealer, where it was diagnosed that the two batteries needed to be replaced. The vehicle was repaired; however, the failure persisted, and the vehicle overheated while driving. The contact stated that GMC OnStar was contacted and informed the contact that diagnostic trouble codes related to the transmissions were retrieved. The vehicle was taken to another dealer Weston Buick GMC (22555 SE Stark St, Gresham, OR 97030) to be diagnosed. The vehicle was being diagnosed. The vehicle was not repaired and remained out of the contact's State of residence. The contact related the failure to an unknown recall; however, the VIN was not included. The manufacturer was notified of the failure and covered vehicle rental expenses that allowed the contact to return to their residence. The contact stated that the vehicle was used for load transportation, and the failure had caused both the contact and her husband to be stranded while delivering loads, which caused lodging expenses and loss of wages. The failure mileage was unknown.

On multiple occasions, the vehicle has suffered from a severe computer failure. This results in the driver information center losing all data, the climate system shutting down, loss of all driver assistance features, loss of computer based safety systems, and prevents the vehicle from shutting down or being restarted until the batteries are disconnected. This results in the driver having no information about speed or engine parameters while driving. This error has not been reproducible by the dealer however they were able to assess it while one error occurred while driving by them. Their diagnostics show a complete failure of all 3 data buses and failure of the serial data gateway. Troubleshooting thus far has been unsuccessful. During the failure, all errors possible are lit on the warning lamps and the driver information center displays warnings for all vehicle modules. The attached photo was taken during one of the events after pulling off the freeway. While traveling at freeway speeds, the information on the screen was the same indicating no speed. This presents numerous safety risks.

The contact owns a 2024 GMC Sierra 3500. The contact stated while driving at various speeds and hauling a trailer, the message "Trailer Brake Disabled - Service Required" was displayed. The vehicle was taken to the dealer, where it was diagnosed and determined that the failure was related to TSB Number: 23-NA-113; however, the part to do the repair was not yet available. The vehicle was not repaired. The manufacturer was not notified of the failure. The failure mileage was approximately 2,390.

The in cab brake controller does not work with electric over hydraulic trailer brakes. In my research to diagnose and fix the problem I find out GMC has known about this for years and has done nothing to correct. I pulled code C1114 and GMC issued a bulletin for part number (K58-036-00) which I purchased and still did not correct this issue. In short there are many 3500 trucks out there running with no trailer brakes. Here is the worst of this problem. If brakes are tested at a stop they appear to work perfectly however once driving this is when the error code is delivered to the truck so the brakes work at a stop when not needed and do not work under driving when they are needed. GMC has ignored this for years and after spending more of my hard earned money for a fix that did not fix the problem. Below I had to choose a date however this has been an issue since first purchase December 5th 2023 to present.