WARNING: This page is about a different car, the 2003 Pontiac Aztek and 2003 Buick Rendezvous. However, it is still accessible from the selected car via links, so may be relevant.
Open the lift gate.
Pull up to remove the door sill plate from the vehicle.
Fig 1: Removing Procedure Of Door Sill Plate - Lift Gate (Rendezvous)