2001 GMC Sierra 1500 Pickup Owner's Manual - Page 141

Exterior Lamps Turn the knob clockwise to the master lamps symbol to turn on all the lamps listed as well as the headlamps. Turn the knob all the way counterclockwise to turn off your lamps and put the system in auto headlamp mode. Automatic Headlamp System When it is dark enough outside, your automatic headlamp system will turn on your headlamps at the normal brightness along with other lamps such as the taillamps, sidemarker, parking lamps and the instrument panel lights. The radio lights will also be dim. Your vehicle is equipped with a light sensor located on the top of the instrument panel in the defroster grille. Be sure it is not covered, or the system will be on whenever the ignition is on. Your parking lamp and headlamp switch is on the driver's side of your instrument panel. Turn the knob clockwise to the parking lamps symbol to manually turn on the following: The system may also turn on your headlamps when driving through a parking garage, heavy overcast weather or a tunnel. This is normal. There is a delay in the transition between the daytime and nighttime operation of the Daytime Running Lamps (DRL) and the automatic headlamp systems so that driving under bridges or bright overhead street lights does not affect the system. The DRL and automatic headlamp system will only be affected when the light sensor sees a change in lighting lasting longer than the delay. D D D D D Parking Lamps Sidemarker Lamps Taillamps License Plate Lamps Instrument Panel Lights 2-58