Circuit/System Description
WARNING: This page is about a different car, the 2007 GMC Sierra and 2007 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The brake fluid level switch monitors the level of brake fluid in the master cylinder. When the instrument panel cluster (IPC) sees the brake fluid level switch input grounded, it turns ON the Red Brake Warning indicator and sends a serial data message to the electronic brake control module (EBCM) indicating the brake fluid level is low.