WARNING: This page is about a different car, the 2005 Buick LaCrosse and 2005 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Power, Ground, and Brake Pressure Modulator Valves Schematic
Courtesy of GENERAL MOTORS CORP.
Fig 2: Indicators, Stop Lamp, Traction Controls, and Serial Data Schematic
Courtesy of GENERAL MOTORS CORP.
Fig 3: Active Brake and Stability Controls (JL4) Schematic