Hey, I also have a 04' Colorado. My brake pedal felt really stiff one day, and before I knew it, I could smell my brakes burning. I had it towed to a brake shop where I know the owner. His mechanic looked it at, and all four brakes were locked. Then out of nowhere, the brakes unlocked and were fine, and I drove it out that day. The next day, I drove it everywhere I needed to go, and on the way home I felt the brake pedal getting stiff again, and yet again, my brakes started to smoke. I pulled over and had it towed to a chevy service department. I heard that the problem could be an ABS sensor, but my ABS light has never come on, nor was my check engine light on. It has been 2 days, and chevy has not come up with a diagnosis. Any ideas on what this problem could be? If you have any ideas, could you give me an estimate of what you would think it would cost tyo fix? I just want to know if this service department is trying to rip me off, just because I have never taken my truck to this chevy service department, and I do not know anybody that works there.