Power Steering Pump
WARNING: This page does not describe the selected car, but rather 35 other vehicles, including the 1999 GMC Yukon, 1999 GMC Suburban, 1999 GMC Sierra, 1999 GMC Savana Special, and 1999 GMC Savana Camper Special. However, it is still accessible from the selected car via links, so may be relevant.
The power steering pump supplies the hydraulic pressure needed to operate the brake booster. The pump is belt-driven. The pump mounts to the engine. The pump provides a continuous fluid flow to the booster when the engine is running.