Circuit/System Verification
WARNING: This page is about a different car, the 2008 Pontiac Torrent and 2008 Chevrolet Equinox. However, it is still accessible from the selected car via links, so may be relevant.
Ignition ON, observe the scan tool Int Trunk/Liftglass Sw. parameter while pressing and releasing the liftgate switch. The parameter should change between Active and Inactive.