One problem related to brake hoses, lines/piping, and fittings has been reported for the 2002 GMC C3500. The most recently reported issues are listed below.
Slowing down to a red traffic light and brake pedal went to the floor. Tried to pump brake pedal to get more pressure but did not work. Drove off onto shoulder and got it slowed down . Drive very slow with hazard lights on to get it back to my house. I was only about a mile away. Got home and looked underneath to find brake fluid all over left rear wheels, fuel tank, left rear shock and drive axle. Continued to look at all brake lines and all of them were corroded bad. Getting prices on having all brake lines replaced.