Two problems related to brake sensor have been reported for the 2004 GMC Sierra. The most recently reported issues are listed below.
Burst steel brake line due to corrosion. Was towing a trailer at the time. All brake lines had to be replaced due to severe corrosion. Still have malfunctioning front abs due to corrosion affecting the wheel sensors.
After exiting onto the highway and attempting to brake to make a right turn I experienced catastrophic brake failure. When the brake pedal was applied there was no pressure, and the pedal went straight to the floor. No warning lights or sensors were activated before the total brake failure. The vehicle was towed to a local GMC dealership. The dealership advised me that the brake line "blew out" from the front left caliper because of rust. I researched such problems and found that similar complaints were numerous and that the NHTSA had initiated an inquiry/investigations into excessive rust on brake components of GMC vehicles causing this type of total brake failure.