One problem related to brake master cylinder has been reported for the 2002 GMC C2500. The most recently reported issues are listed below.
Steel brake line ruptured with no warning under the drivers side floor panel. It was the line from the master cylinder to the anti-lock brake actuator. Read dozens of online postings about this being a huge problem and was encouraged to report it. Safely stopping the truck (empty) was very hard and I couldn't imaging what would have happened if I had been pulling a trailer, which is very common on this truck.