GM Service Manual Online
For 1990-2009 cars only

This feature turns on the low-beam headlamps, instrument panel cluster backlighting and taillamps when the windshield wipers have been in use for about six seconds.

If the wiper activated headlamps are on and the ignition switch is turned to RUN, the wiper activated headlamps will continue. When you turn the key to OFF, the wiper activated headlamps will immediately turn off. The wiper activated headlamps will also turn off if you turn off the windshield wipers.