GM Service Manual Online
For 1990-2009 cars only

If a door is open, a reminder chime will sound when your headlamps or parking lamps are manually turned on and your key is out of the ignition. To turn off the chime, turn the headlamp switch to off or AUTO and then back on. In the automatic mode, the headlamps turn off once the ignition is in LOCK and the headlamp delay ends (if enabled in the DIC).