Theory Of Operation
WARNING: This page is about a different car, the 2016 RAM 1500. However, it is still accessible from the selected car via links, so may be relevant.
The Vehicle Speed Sensor (VSS) signal is transmitted to the Anti-Lock Brake System (ABS) Module via dedicated hard wire. The VSS signal is then transmitted over the Controller Area Network (CAN) bus to the Transmission Control Module (TCM).
The Output Speed Sensor signal is a direct input to the TCM.
The TCM monitors these signals to determine if the VSS signal CAN message is valid. If the VSS signal and the Output Speed Sensor signal do not match, this Diagnostic Trouble Code (DTC) is set.