Theory Of Operation
WARNING: This page is about a different car, the 2016 RAM 3500 HD and 2016 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 Rear Lighting Fault Sense circuit to the Tail Lamp Assemblies. When the Turn Signal is activated, an internal driver in the Tail Lamp Assemblies will pull the reference voltage signal low in sequence with the Turn Signal flash.