Circuit/System Description
WARNING: This page is about a different car, the 2007 GMC Sierra and 2007 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The body control module (BCM) energizes the unlock relay coil through a low side drive control circuit. When the BCM receives an unlock message the door unlock control circuit is grounded energizing the unlock relay coil.