2004 GMC Yukon Owner's Manual - Page 173

; (Parking Lamps): Turning the control to this position turns on the parking lamps, together with the following: Sidemarker Lamps Taillamps License Plate Lamps Instrument Panel Lights Roof Marker Lamps (If Equipped) 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. 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. 5 (Headlamps): Turning the control to this position turns on the headlamps, together with the previously listed lamps and lights. You can switch your headlamps from high to low-beam by pushing the turn signal/high-beam lever towards the instrument panel. A circuit breaker protects your headlamps. If you have an electrical overload, your headlamps will flicker on and off. Have your headlamp wiring checked right away if this happens. 3-15