2006 GMC Yukon Owner's Manual - Page 177

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. If you start your vehicle in a dark garage, the automatic headlamp system will come on immediately. Once you leave the garage, it will take approximately one minute for the automatic headlamp system to change to DRL if it is bright enough outside. During that delay, your instrument panel cluster may not be as bright as usual. Make sure your instrument panel brightness control is in the full bright position. See Instrument Panel Brightness on page 3-19. To idle your vehicle with the automatic headlamp system off, turn the control to the off position. You may be able to turn off your Automatic Headlamp System. See Daytime Running Lamps (DRL) on page 3-16 for more information. Your headlamps will also stay on after you exit the vehicle. You can program this feature using the Driver Information Center (DIC). See DIC Vehicle Customization on page 3-67. As with any vehicle, you should turn on the regular headlamp system when you need them. 3-17