2009 GMC Yukon Owner's Manual - Page 200

When the headlamps are turned on while the vehicle is on, the headlamps will turn off automatically 10 minutes after the ignition is turned off. When the headlamps are turned on while the vehicle is off, the headlamps will stay on for 10 minutes before automatically turning off to prevent the battery from being drained. Turn the headlamp control to off and then back to the headlamp on position to make the headlamps stay on for an additional 10 minutes. The DRL system will come on when the following conditions are met: The ignition is on. The exterior lamps control is in AUTO. The transmission is not in P (Park). The light sensor determines it is daytime. Headlamps on Reminder A reminder chime will sound when the headlamps or parking lamps are manually turned on and the ignition is off and a door is open. To disable the chime, turn the light off. When the DRL are on, only the DRL lamps will be on. The taillamps, sidemarker, instrument panel lights, and other lamps will not be on. When it begins to get dark, the automatic headlamp system will switch from DRL to the headlamps. To turn off the DRL lamps, turn the exterior lamps control to the OFF position and then release. For vehicles first sold in Canada, the transmission must be in the P (Park) position, before the DRL lamps can be turned off. Daytime Running Lamps (DRL) Daytime Running Lamps (DRL) can make it easier for others to see the front of your vehicle during the day. Fully functional daytime running lamps are required on all vehicles first sold in Canada. 3-16