Theory Of Operation
WARNING: This page is about a different car, the 2015 RAM 3500 HD and 2015 RAM 2500 HD. However, it is still accessible from the selected car via links, so may be relevant.
The Brake Switch signal must be active before the Shift Lever can be moved out of the Park position. When the Brake Pedal is applied, the Body Control Module (BCM) receives a Controller Area Network (CAN) message from the Anti-lock Brake System (ABS) Module. Based on the Gear Selector position, the BCM then provides battery voltage to the Gear Selector to activate the Brake Transmission Shift Interlock (BTSI) solenoid.