Switch, Stop Lamp: Operation

The brake (or stop) lamp switch controls independent circuits. These circuits are described as follows:

• Normally Closed  - The normally closed circuit provides a hardwired output to the Body Control Module (BCM) indicating the position of the brake pedal, depressed or released. The BCM responds by relaying electronic brake switch status  messages over the Controller Area Network (CAN) data bus to other electronic modules in the vehicle.
• Normally Open  - The normally open circuit provides hardwired outputs to the BCM and the Powertrain Control Module (PCM) whenever the brake pedal is depressed. The BCM responds to the normally open input by providing a control output that energizes or deenergizes the brake lamps.

The brake lamp switch as well as the hardwired inputs and outputs of the switch may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. However, the switch can only be tested while installed and, while in the installed position, the switch terminals are inaccessible to test meter probes. The most reliable, efficient and accurate means to diagnose the electronic controls and communication related to brake lamp switch operation requires the use of a diagnostic scan tool to read the switch status through the BCM. Refer to the appropriate diagnostic information.