Symptoms - Hydraulic Brakes: Intermittent
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, 2004 Chevrolet Cab & Chassis Silverado, and 2003 GMC Sierra. However, it is still accessible from the selected car via links, so may be relevant.
Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.