Checking and Adding Fluid
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.
For information on checking and adding fluid to the hydraulic booster system, refer to Checking and Adding Power Steering Fluid (Without Hydroboost) or Checking and Adding Power Steering Fluid (With Hydroboost) in Power Steering System.