Check the fuse. Then check the wiring.
If you are referring to the brake light then the brake light switch is stuck.
9006 for long and 9005 for short
how to change third or center brake light on Chevy beretta 95
needs new alternator
The brake light switch is broken or out of adjustment.
The brake lights on a 96 Jimmy are operated by the brake light switch, mounted on the brake pedal assembly. If the switch is bad the lights could stay on or off, or be sporadic.
Location? Usually at the upper end of the brake pedal (under dash)
when this light is on it means that there is something wrong with your anti-lock-brake system and you should go get it checked.
Is the brake fluid level low in your brake master cylinder in the engine compartment ?
brake light switch above the brake pedal
under the dash in the fuse box