2000 GMC Yukon Owner's Manual - Page 121

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. To idle your vehicle with the automatic headlamp system off, set the parking brake while the ignition is off. Then start your vehicle. The automatic headlamp system will stay off until you release the parking brake. As with any vehicle, you should turn on the regular headlamp system when you need it. You may be able to turn off your Automatic Headlamp System. See "Daytime Running Lamps (DRL)" later in this section for more information. Lamps On Reminder A reminder chime will sound when your headlamps or parking lamps are manually turned on and your ignition is in OFF, LOCK or ACCESSORY. To disable the chime, rotate the thumbwheel all the way down. In the automatic mode, the headlamps turn off once the ignition key is in OFF. Daytime Running Lamps Daytime Running Lamps (DRL) can make it easier for others to see the front of your vehicle during the day. DRL can be helpful in many different driving conditions, but they can be especially helpful in the short periods after dawn and before sunset. The DRL system will come on when: D D D D D the ignition is on, the headlamp switch is in automatic headlamp mode, the automatic transmission is not in PARK (P), the light sensor determines it is daytime and the parking brake is released. When the DRL are on, only your DRL lamps will be on. The taillamps, sidemarker and other lamps won't be on. The instrument panel won't be lit up either. 2-44