Theory of Operation
WARNING: This page is about a different car, the 2011 RAM Pickup and 2011 RAM Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
The Transmission Control Output is used to supply the primary power to the Transmission Control Module (TCM). When the ignition switch is in the unlock, run or crank position, the ignition switch provides and input to the Totally Integrated Power Module (TIPM). The TIPM then energizes the Transmission Control relay which provides voltage to the TCM.