Battery voltage is applied through the 10A GAUGES FUSE 4 to the brake indicator when the ignition switch is in RUN, BULB TEST, or START positions. The brake indicator can be lit by having ground applied to it from any of the following modules:

The brake indicator will light whenever the parking brake is engaged. When the parking brake is engaged, ground is supplied through the closed contacts of the park brake warning switch to the brake indicator. The brake indicator lights to alert the driver that the park brake is engaged.

The brake indicator will light when the ignition switch is turned from the LOCK to RUN position. This is when the electronic brake control module (EBCM) conducts its initial test which entails lighting the brake indicator and the ABS indicator. The electronic brake control module (EBCM) will also light the brake indicator if there is a malfunction within the four wheel antilock brake system which is affecting the operation of the base hydraulic braking system.

The brake indicator will light if there is low brake fluid pressure in the front or rear brakes. When the brake pressure warning switch senses low brake fluid pressure in the front or rear brakes, it closes the brake pressure warning switch. A ground is supplied through the closed contacts of the brake pressure warning switch to the brake indicator. With both power and ground applied to the brake indicator, it will light.

All of the functions are monitored and enabled by the body control module via the Class 2 data lines.