GM Service Manual Online
For 1990-2009 cars only

If a door is open, a reminder chime will sound when the headlamps or parking lamps are manually turned on and the key is out of the ignition. To turn off the chime, turn the headlamp switch to off or AUTO and then back on, or close and re-open the door. In the AUTO mode, the headlamps turn off once the ignition is in LOCK/OFF or may remain on until the headlamp delay ends (if enabled in the DIC). See "Exit Lighting" under DIC Vehicle Customization.