Thompson2008

I need help! I have a 2015 GMC Sierra in normal driving conditions on flat surfaces my grade braking activates when I am not accelerating. I have had it to the dealership several times for this and they have replaced the pcm, brake pedal switch and cleaned some connections. This only worked for short period of time each time. They say the computer shows the brake pedal is being depressed is why it is activating, then they will recalibrate it and good for a week of so. I know I can Deactivate the grade braking by pressing and holding The tow haul button. This works for a while and then the truck will go into a limp mode. The dealership is lost I am lost and any help would be much appreciated