Theory Of Operation
WARNING: This page is about a different car, the 2016 Dodge Durango. However, it is still accessible from the selected car via links, so may be relevant.
When the Body Control Module (BCM) receives an input from the Headlamp Switch, requesting Park Lamp illumination, the BCM provides a voltage output through the Rear Park Lamp Driver circuit to the Tail Lamp Assemblies. A ground path for the Park Lamps is present through the harness to the body sheet metal.