GM Service Manual Online
For 1990-2009 cars only

To turn the headlamps off when it is dark outside, turn the exterior lamps control to the parking lamp position. In this position, the parking lamps, sidemarker lamps, taillamps, license plate lamps and instrument panel lights will be on, but the headlamps will be off.

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