Electric Auto/Apply System Bleeding
WARNING: This page does not describe the selected car, but rather 30 other vehicles, including the 1998 Pontiac Trans Sport, 1998 Oldsmobile Silhouette, 1998 Oldsmobile Bravada, 1998 GMC Yukon, and 1998 GMC Suburban. However, it is still accessible from the selected car via links, so may be relevant.
Check fluid level with engine off and transmission in Park. Fluid level should be up to the FULL mark on reservoir. Fill reservoir with Dexron III ATF, as necessary.