STOPLAMP Switch
WARNING: This page does not describe the selected car, but rather 11 other vehicles, including the 1991 Pontiac Grand Prix, 1991 Oldsmobile Cutlass Supreme, 1991 Chevrolet Lumina, 1991 Buick Regal, and 1990 Pontiac Grand Prix. However, it is still accessible from the selected car via links, so may be relevant.
Disconnect negative battery cable. Depress brake pedal as far as possible and hold. Using a stiff wire with a hooked end, gently pull on the switch set lever and listen for an audible click. If no click is heard, switch may be defective.