Visual/Physical Inspection
WARNING: This page does not describe the selected car, but rather 12 other vehicles, including the 2002 GMC Savana Special, 2002 GMC Savana Camper Special, 2002 GMC Savana, 2002 Chevrolet RV Cutaway, and 2002 Chevrolet Cutaway. However, it is still accessible from the selected car via links, so may be relevant.
Inspect for aftermarket devices which could affect the operation of the automatic transmission shift lock control system. Inspect easily accessible or visible system components for obvious damage or conditions which could cause the symptom.