Except Aztek, Montana, Silhouette & Venture
WARNING: This page does not describe the selected car, but rather 46 other vehicles, including the 2001 Pontiac Montana, 2001 Pontiac Aztek, 2001 Oldsmobile Silhouette, 2001 Oldsmobile Bravada, and 2001 GMC Sonoma. However, it is still accessible from the selected car via links, so may be relevant.
Pressure differential warning switch in combination valve energizes brake warning light on instrument panel when front or rear brakes lose hydraulic pressure. After repairing failed side of hydraulic system, depress brake pedal with moderate to heavy pressure to hydraulically center the piston. This will turn off brake warning light. On vehicles with Hydro-Boost, insufficient flow of power steering fluid to the hydraulic booster system will turn on brake warning light.