Brake Light Switch: Description and Operation

DESCRIPTION
The plunger type stop lamp switch is mounted on a bracket attached to the brake pedal support. The switch can be adjusted when necessary.

PURPOSE
The primary function of the switch is to turn on the stop lamps during braking. The switch is also used to send signals to components that must know when the brakes are applied, such as the Powertrain Control Module (PCM), which uses the signal to cancel speed control.

OPERATION
Vehicles equipped with the speed control option use a dual function stop lamp switch. The switch is mounted in the same location as the conventional stop lamp switch, on the brake pedal mounting bracket under the instrument panel. The PCM monitors the state of the dual function stop lamp switch. Refer to Lighting and Horns/Brake Light Switch for more information on stop lamp switch service and adjustment procedures.

The Controller Antilock Brake (CAB) uses the brake switch signal to monitor brake pedal application. When the switch contacts open (brakes applied), the CAB receives the brake applied signal. The CAB then monitors the ABS system to anticipate the need for an ABS stop.

CIRCUIT OPERATION
Rear Wheel
Circuit V40 provides an input to the Controller Anti Lock Brake (CAB) as to when the operator is applying the brakes. The V40 circuit connects to cavity 7 of the CAB.

All Wheel
On circuit V40, the Controller Anti Lock Brake (CAB) senses when the brake pedal has been pressed. Circuit V40 connects to cavity 9 of the CAB and splices to the stop lamp switch and the Power-train Control Module (PCM).