Battery Rundown Protection / Inadvertent Power
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 body control module (BCM) controls the lighting system through circuits that enable both the exterior lamp functions of the park lamps, the headlamps, and the fog lamps, as well as the interior lamps. The BCM opens these enabling circuits 20 minutes after the ignition switch is turned OFF with no lamp switch activity. If the ignition switch is turned to any position other than OFF, or if a lamp switch is activated during this 20-minute period, the timer resets for another 20 minutes.