2003 GMC Yukon Owner's Manual - Page 171

When it begins to get dark, the automatic headlamp system will switch from DRL to the headlamps or the last chosen headlamp setting that was used. When you turn the headlamp switch off, the headlamps will go off, and your DRL lamps will illuminate, provided it is not dark outside. Shifting the transmission into PARK (P) will allow you to idle the vehicle with the DRL off. The DRL will stay off until you shift the transmission out of PARK (P). This procedure applies only to vehicles first sold in the United States. Your parking lamps and/or low-beam headlamps must be on for your fog lamps to work. Press the button to turn the fog lamps on. Press the button again to turn them off. An indicator light will glow in the button when the fog lamps are on. Remember, fog lamps alone will not give off as much light as your headlamps. Never use your fog lamps in the dark without turning on your headlamps. The fog lamps will go off whenever your high-beam headlamps come on. When the high beams go off, the fog lamps will come on again. The fog lamps will be cancelled after the ignition is turned off. If you still want to use the fog lamps after you restart the vehicle, you will need to press the fog lamp button again. Fog Lamps If your vehicle has fog lamps, use them for better vision in foggy or misty conditions. The fog lamp button is located on the left side of the instrument panel. Auxiliary Roof Mounted Lamp Switch If your vehicle has this feature, this switch includes wiring provisions for a dealer or a qualified service center to install an auxiliary roof lamp. 3-17