Cargo Lamp
WARNING: This page is about a different car, the 2004 Pontiac Aztek and 2004 Buick Rendezvous. However, it is still accessible from the selected car via links, so may be relevant.
The courtesy lamps supply voltage circuit also provides battery positive voltage to the cargo lamp. When the rear compartment is opened, its switch closes to provide a ground circuit and the cargo lamp illuminates.