The Pontiac Grand Prix uses a screw-in type of switch located in a bracket behind the top-side of the brake pedal arm. It is essentially just an on and off switch. When the plunger is pushed in, as is the case when the brake pedal is all the way up, the switch turns open. As the brake pedal is depressed, the arm extends the plunger in the switch, which closes the switch; this allows power to travel to the taillights, turning them on.
Remove the electrical connector from the brake light switch. A flashlight will be necessary to see the switch, since it is behind the dash. Lie on the driver's side floor so that you can see the top of the brake pedal arm. There will be a while plastic button-type switch in a bracket toward the backside top of the brake pedal arm. Use the needle-nose pliers to work the electrical connector off of the switch.
Remove the brake light switch by using the right arm to slightly depress the brake pedal while using regular pliers to loosen the white plastic nut on the brake light switch. The plastic nut is used as a lock nut to hold the brake light switch in the proper position. Once loosened, unscrew the brake light switch from the bracket.
Install the lock nut on the new brake light switch if it does not come with one. Screw the brake light switch into the bracket, making sure that the brake pedal arm is all the way out. Screw the switch in to the point that the button on the switch comes into contact with the brake pedal arm enough to depress the button all the way in. Run the nut into the bracket and tighten sufficiently so that the switch will not move by twisting. Connect the electrical connector.
Check to see if the taillights come on when the pedal is first depressed. If the pedal needs to be depressed too far before the brake lights come on, loosen the locknut, back the switch out a little and try again.
