Today brake pedal was softer than usual this morning. The truck has had a brake failure light on the dash since I got it. The early GM dealer diagnostics said it was a bad proportioning valve, but the part is discontinued. Today I could feel the brakes hanging a little after about an hour of running errands around town. At 10:30 am I was taking a corner in a parking lot at about 3 mph and the left rear , ebrake wheel hung up and stopped the truck right in traffic. I shifted to 4 dig and the front wheels pulled the truck 10 feet to get out of traffic.
I sat for 4 hours waiting on AAA tow truck, they sent 3 different roll back flat beds even though I told them 6 times I needed a lift and dolly truck because it is 4wd and rear wheel is locked and I don’t want to drag onto a rollback. AAA finally says after 4 hours they have no lift and dolly trucks in my area. So I start playing with the e brake, smash it to the floor and hear a loud pop. That pop freed up the wheel and i was able to drive again. Went 3 miles straight to GMC dealer, threw them the keys and said rear drums and e brake locked up today and pedal is soft, call me when you have it figured out.
Any thoughts on what it is? Remember we already know the dash code is throwing a bad proportion valve.