Circuit/System Description
WARNING: This page is about a different car, the 2017 GMC Acadia. However, it is still accessible from the selected car via links, so may be relevant.
The liftgate control module will receive a serial data message from the body control module that the backlights for the interior switches have been commanded ON, the liftgate control module in response will provide voltage to the backlight within the liftgate close switch.