WARNING: This page is about a different car, the 2003 Pontiac Montana, 2003 Oldsmobile Silhouette, and 2003 Chevrolet Venture. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Rear of Vehicle Low - Diagnostic Chart (1 Of 2)
Courtesy of GENERAL MOTORS CORP.
Fig 2: Rear of Vehicle Low - Diagnostic Chart (2 Of 2)