Circuit/System Verification
WARNING: This page is about a different car, the 2011 Buick Regal. However, it is still accessible from the selected car via links, so may be relevant.
Ignition ON, observe the scan tool Trunk Lid/Liftgate Window Exterior Unlatch Switch parameter while pressing and releasing the S58A rear compartment lid unlatch switch-exterior. The parameter should change between Active and Inactive.