2001 GMC Sierra 1500 Pickup Owner's Manual - Page 142

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. You may be able to turn off your automatic headlamp system. See "Daytime Running Lamps (DRL)" later in this section for more information. As with any vehicle, you should turn on the regular headlamp system when you need it. The DRL system will come on when the following conditions are met: 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. 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, turn the thumbwheel all the way down. In the automatic mode, the headlamps turn off once the ignition key is in OFF. 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. To idle an automatic transmission equipped vehicle with the DRL off, set the parking brake. Shifting the transmission into PARK (P) will also allow you to idle the vehicle with the DRL off. The DRL will stay off until you release the parking brake or shift the transmission out of PARK (P). 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. Fully functional daytime running lights are required on all vehicles first sold in Canada. 2-59