Theory Of Operation
WARNING: This page is about a different car, the 2012 Dodge Caliber. However, it is still accessible from the selected car via links, so may be relevant.
The Transmission Control Module (TCM) monitors the brake switch 3 signal over the CAN Bus from the Totally Integrated Power Module (TIPM). If the Transmission is shifted into Drive position without confirming that the brake was depressed before the shift, a DTC will set.