Try adjusting the switch.
Measure the clearance between the outer case of the stop lamp switch and brake pedal (Figure 1). The clearance is 0.5 to 1.5 mm (0.020 to 0.060 in).
If the clearance is not within specifications, proceed with the adjustment procedure.
Disconnect the brake switch connector, and loosen the lock nut (old style) or turn the stop lamp switch 1/4 turn counterclockwise to loosen it (new style).
Move the switch so the distance between the pedal stopper and outer case is between 0.5 - 1.5 mm (.020 - .060 in.).
Tighten the lock nut or twist the switch 1/4 turn clockwise to lock it in place. Recheck clearance after tightening.
Re-connect the brake switch connector.
Check stop light operation. Make sure the brake lights are not illuminated with the brake pedal released.
:A RUNNING CHANGE WAS MADE TO THE TYPE OF STOP LAMP SWITCH USED ON 1998 OR LATER VEHICLES. EITHER THE ADJUSTMENT WILL BE MADE BY LOOSENING AND ADJUSTING A LOCK NUT OR BY TWISTING THE SWITCH FROM ITS BAYONET STYLE NUT, MOVING THE SWITCH TO THE PROPER POSITION, AND TWISTING IT BACK TO ITS LOCKED POSITION.