Circuit/System Description
WARNING: This page is about a different car, the 2007 Suzuki XL7. However, it is still accessible from the selected car via links, so may be relevant.
The headlamp switch of the multifunction switch controls the ground for the body control module (BCM). The BCM monitors the park lamp switch signal. Once the BCM senses a voltage drop on the park lamp switch signal the BCM supplies a ground to the headlamp relay control circuit. The headlamp relay than supplies a ground to the headlamp circuit thus turning on the headlamps. Both the high and low beam headlamp relays are soldered to the underhood fuseblock.