GM Service Manual Online
For 1990-2009 cars only
Park Brake Switch: The scan tool displays the current state of the parking brake switch as seen by the BCM. With the parking brake applied, the scan tool displays Applied.

Brake Fluid Level Sensor: The scan tool displays the current state of the brake fluid level sensor as reported to the EBCM by the IPC. When brake fluid is below the minimum level, the scan tool displays Low.