When starting the vehicle, I got a message to service the parking brake (this is the second time I-??ve had this warning appear in the 21,000 miles I-??ve owned it, first was approximately 5,000 miles ago). When this warning is active the parking brake does not engage, and can-??t be used to stop the vehicle when the brakes fail as they did today. With 42,774 miles on the vehicle, and the onboard monitor for brake wear showing remaining brake life at 94% front and 96% rear, brake fluid reservoir between Max and Min the brake pedal went soft and the vehicle would not stop. I resorted to putting the vehicle in neutral and pumping the brakes until the pedal got hard. As soon as I let off the brake my vehicle began to roll backwards, stepped on the brake pedal again and the pedal again went to the floor without stopping or slowing the vehicle (pumping the brakes got it stopped again inches away from running into my house). The myGMC app notified me that I need to service the ABS system. I had the vehicle towed to the dealership for diagnostics and repair. Possibly related, this afternoon before the brakes stopped working I felt a mild vibration when traveling 20-35mph that resembled the vibration that occurs when a wheel bearing has begun to fail. Tow truck driver witnessed the vehicles inability to stop when putting it in neutral to load vehicle. It is unimaginable that a vehicle can be placed on the highway that has no backup system in the event of brake failure. Had a kid run out in front of me there would have been no way to avoid the accident (no other warnings appeared to indicate the vehicle was unsafe to drive. Brakes worked correctly and stopped appropriately until they didn-??t).

- Grangeville, ID, USA

The throttle body gets stuck wide open after the eninge gets up to operating temperature, it will give some warning with the throttle like on off throttle use and no codes show up at all. The risk of everyones is in extrem DANGER. The break are to soft and well not stop unless you put both feet on the break pedal down to the floor. Tranismission can NOT figure out what gear it needs to be in way too many gears and horrible fuel mpg for the 6.6L Duramax L5P. None of the GM dealership will look at the truck unless there is a code or it is happening right there when they look up the trucks VIN.

- Rocklin, CA, USA

The vehicle recently had a recall repaired at the dealership. I subsequently took delivery on it as a BRAND NEW UNIT, and the brakes are extremely soft; to the point where I must depress the pedal to the floor to get it stopped even at slow speeds. I hoped it was just an air bubble from the repair; but the fluid levels are full and the dealer had no ideas on what could be wrong at this point. I have a great relationship with this dealer, and we-??ll continue working on it. But GM is releasing absolute trash lately and I fear that some poor family will load up, trusting these vehicles, and be badly injured or killed. After 200 miles of driving it back to my residence, both at highway speeds and residential road speeds, these brakes have not improved; ruling out an air bubble. I-??m worried it may be associated with the recall that was previously remedied.

- Fowler, CO, USA

Trailer brake wiring connection continually disconnectsthen reconnects some time later. Some periods of up to 10 minutes without having trailer braking power. Major safety issue when toeing fifth wheel trailer. We lost brakes going down steep grades. GMC is aware of issue, but has not provided a solution. Vehicle has been yo service shop with no resolution. Case has been opened with GMC.

- Olympia, WA, USA