Combination Valve Replacement: Notes
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.
IMPORTANT:
Note the identification code on the combination valve. The new valve must have the same identification number as the old valve.