Bring to a shop that has an ABS scanner to determine the problem
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.
The running lights will turn off when the emergency brake is on by tripping a switch connected to the emergency brake. Pushing in the emergency brake slightly will do the trick, but make sure you don't push in too far or you will be driving with the emergency brake on!
The only way you can completely turn off the headlights is to push in the emergency brake slightly, then start the truck and leave the emergency brake on the slightest setting, and the running lights will stay off. Obviously the brakes will be slightly engaged, but you can adjust the emergency brake so the first click doesn't engage the brakes.
If emergency brake is on 1 click it turns daytime running lights off. Pull out on emergency brake handle and see if this fixes the problem.
it may need some brake fluid
SLIGHTLY DEPRESS EMERGENCY BRAKE TILL LIGHTS GO OUT DON"T FULLY DEPRESS THEM JUST ENOUGH TO TURN OUT LIGHTS OR ADJUST THE SWITCH AT THE EMERGENCY BRAKE PEDAL TILL THE GO OUT
Under the dash up above the emergency brake pedal.
Check the brake light switch. It's probably attached to the brake pedal, under the dashboard.
Brake Lights "Stuck" ONUsually that is caused by the brake light switch becoming "out of adjustment," but sometimes it can be caused by a defective brake light switch.
Check the bulbs - they are doubloe filamented with the smaller being for brake/turn signals Check the fuses
Because your brake system is not working properly. You need to have your brake system checked out and repaired before you have to make an emergency stop and then they fail to brake as they should. ALWAYS DRIVE SAFELY
The GMC dash tail and parking lights are on a different fuse from the brake lights. Check the fuses for a possible blown fuse.