F 550 2WD Super Duty V8-7.3L DSL Turbo VIN F (2002)
Brake Signal: Description and Operation
Brake Lamp Switch
The Brake Lamp Switch signals the PCM with a battery positive voltage (B+) signal whenever the vehicle brake pedal is applied.
The signal informs the PCM to disengage the torque converter clutch, speed control and auxiliary idle control (if equipped).
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 Brake Lamp switch has failed.