Theory Of Operation
WARNING: This page is about a different car, the 2006 Dodge Magnum, 2006 Dodge Charger, and 2006 Chrysler 300. 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. The Electronic Shift Module (ESM) receives two brake switch signals. The first signal is a CAN C BUS message is from the ABS and the second signal is a hard wired brake switch signal to the ESM. The CAN C Bus message is the primary brake switch signal and the hard wired signal serves as the backup brake switch signal.