Brake Light Bulb: Description and Operation

The brake system indicator light comes ON to alert the driver that the parking brake is applied, or that the brake fluid level is low. It also comes ON as a bulb test when the engine is cranked.

Bulb Check
With the ignition switch in START (III), voltage is applied through fuse 9 to the bulb check circuit. The bulb check circuit closes, allowing current to flow through the brake indicator system indicator light and bulb check circuit to ground. The brake system indicator light then comes ON to test the bulb.