Theory Of Operation
WARNING: This page is about a different car, the 2017 Jeep Cherokee. However, it is still accessible from the selected car via links, so may be relevant.
When Low Beam Lamp illumination is selected, the Headlamp Switch sends an input to the Body Control Module (BCM). The BCM provides a Pulse Width Modulated (PWM) voltage, through the Left and Right Low Beam Driver circuits, to the Left and Right Front Lamp Assemblies. A separate ground circuit is provided to the Low and High Beam Lamps through the wiring harness.