GM Service Manual Online
For 1990-2009 cars only

This feature works when the ignition is in the ON/RUN position and it is dark outside. To turn the headlamps off when it is dark outside but keep other exterior lights on, turn the exterior lamp control to the parking lamp position.

To turn on the headlamps along with the other lamps when it is dark outside, turn the exterior lamp control to the AUTO or headlamp position.

This function does not work for vehicles first sold in Canada.