Three problems related to brake light on have been reported for the 2003 GMC Sierra. The most recently reported issues are listed below.
While traveling in my 2003 GMC Sierra truck at approximately 45 mph I stepped on the brake pedal to stop at a stop sign and the pedal went 3/4 of the way down to the floor, then the brake light came on and the truck did not stop as quickly as it usually does ( glad I was not going any faster) . Upon checking the truck it was discovered that the front drivers side steel brake line had a hole in it due to corrosion and there was no brake fluid in the master cylinder .
I was parked on a sloped driveway (about 10 - 15 degrees). I started the engine, stepped on the brake pedal and took the car out of park into drive. Brake pedal was normal. I started to roll forward and when I pushed the brake pedal the car did not slow. I slammed the brake pedal and it went all the way to the floor. At this point I went off the end of the driveway onto a 45 degree downward sloped lawn; then into a wooded area at the top of a ravine. I slammed into a tree. The car was judged a total loss by my insurance company. I did not get a brake warning light. The airbags did not deploy. The car was serviced at a union park GMC (wilmington, DE) two days prior. Including brake inspection. Cause of brake failure was determined to be ruptured brake line. Both front and rear brakes were failed.
Pulled up to the carwash. As I was preparing to put money in the machine,I heard a hissing sound. Brake pedal went to the floor & brake light came on. I had no brakes whatsoever. Was able to roll back to a vacant area & stop with emergency brake. Truck is still in the shop where mechanic is replacing all the brake lines. He said this was common for this truck & the lines were all bad.