Brake Signal: Description and Operation

DESCRIPTION - BRAKE SWITCH
The brake switch is normally closed and opens when the brake pedal is depressed. When closed, the switch conducts battery voltage to a terminal of the PCM. When the brake is depressed, the switch opens and voltage in the circuit goes to zero, indicating the brakes are being applied. The PCM may respond to this input by disabling the torque converter clutch, turning cruise control "OFF", or modifying other outputs like downshifting the transmission (auto trans only).