GM Service Manual Online
For 1990-2009 cars only

This feature activates the headlamps and parking lamps after the windshield wipers have been in use for about six seconds. For this feature to work, automatic lighting must be enabled. See Headlamps for additional information.

When the ignition is turned off, the wiper-activated headlamps will immediately turn off. They will also turn off if the windshield wiper control is turned off.