Battery Rundown Protection/Inadvertent Power
WARNING: This page is about a different car, the 2006 Pontiac Montana SV6, 2006 Chevrolet Uplander, and 2006 Buick Terraza. 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 headlamps and the courtesy lamps. If one of these lamps is left ON, battery rundown protection/inadvertent power feature will turn OFF the lamps 20 minutes after the ignition switch is turned to the OFF position. If the ignition switch is turned to any position other than OFF or if a lamp is activated during this 20-minute period, the circuits will then be enabled.
If the headlamp switch is placed in the HEAD position after the ignition switch has been turned OFF or if the ignition switch is in the ACCY position, the headlights will remain ON until turned OFF or the battery runs dead.