Brake Signal: Description and Operation

Typical Brake Pedal Position Switch:

PURPOSE
The signal informs the Powertrain Control Module (PCM) to disengage the torque converter clutch.

On certain applications, the PCM adjusts the engine idle speed with the brakes applied and the A/C turned On, or turns the A/C Off after a calibrated time.

OPERATION
The Brake On/Off Switch (BOO) signals the PCM with a battery voltage (B+) signal whenever the vehicle brakes are applied.

If all the stoplamp bulbs are burned out (open), a high voltage is present at the PCM due to a pull-up resistor in the PCM. This provides fail safe operation in the event the circuit to the BOO switch has failed.