Circuit Description
WARNING: This page is about a different car, the 2002 Chevrolet Malibu. However, it is still accessible from the selected car via links, so may be relevant.
The body control module (BCM) turns on the park lamp relay when the ambient light sensor senses a dark condition. Battery positive voltage is supplied to the park lamp relay at all times through the PARK LPS fuse. The BCM grounds the park lamp relay control circuit in order to activate the relay.