Theory Of Operation
WARNING: This page is about a different car, the 2017 RAM 2500 HD. However, it is still accessible from the selected car via links, so may be relevant.
When the ignition is on, the Body Control Module (BCM) provides a reference voltage signal through the Left and Right Fault Sense circuits to the Left and Right Tail Lamp Assemblies. When a Left and Right Turn Signal is activated, an internal driver in the Left and Right Tail Lamp Assemblies will pull the reference voltage signal low in sequence with the Turn Signal flash.