2003 Chevrolet Tahoe Owner's Manual - Page 166

Daytime Running Lamps Daytime Running Lamps (DRL) can make it easier for others to see the front of your vehicle during the day. BRL can be helpful in many different driving conditions, but they can be especially helpful in the short periods after dawn and before sunset. Fully functional daytime running lamps are required on all vehicles first sold in Canada. The DRL system will come on when the following conditions are met: the ignition is on, the exterior lamps control is AUTO, the automatic transmission is not in PARK (P), the light sensor determines it is daytime and 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. 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. 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. Your parking lamps and/or low-beam headlamps must be on for your fog lamps to work. 3-15