1998 Buick Century Owner's Manual - Page 120

Delayed Exit Lighting This featureilluminates your vehicle's interior for a period of time afterthe ignition key is removed from the ignition. The vehicle's ignition must be off for Delayed Exit Lighting to work. When the ignition key is removed, interior illumination will activate and remain on until: The ignition is in RUN. The power door locks are activated. An illumination period of 25 seconds has elapsed. If during theillumination period a door is opened, the timed illumination period will be canceled and the interior lamps will remain on since a door is open. Rearview Mirror Reading Lamps (If Equipped) Use the switch next to each lamp to turn them on and off. 2-44