2009 Chevrolet Suburban 2500 Owner's Manual - Page 205

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 is only affected when the light sensor detects a change in lighting lasting longer than the delay. If the vehicle is started in a dark garage, the automatic headlamp system will come on immediately. Once the vehicle leaves the garage, it takes approximately one minute for the automatic headlamp system to change to DRL if it is bright enough outside. During that delay, the instrument panel cluster may not be as bright as usual. Make sure the instrument panel brightness control is in the full bright position. See Instrument Panel Brightness on page 3-18. To idle the vehicle with the automatic headlamp system off, turn the control to the off position. The headlamps will also stay on after you exit the vehicle. This feature can be programmed using the Driver Information Center (DIC). See DIC Vehicle Customization (With DIC Buttons) on page 3-74. The regular headlamp system can be turned on when needed. Fog Lamps For vehicles with fog lamps, the control is located next to the exterior lamps control on the instrument panel, to the left of the steering column. The ignition must be in the ON/RUN position for the fog lamps to come on. # (Fog Lamps): Press to turn the fog lamps on or off. A light will come on in the instrument panel cluster. When the fog lamps are turned on, the parking lamps automatically turn on. When the headlamps are changed to high-beam, the fog lamps also go off. When the high-beam headlamps are turned off, the fog lamps will come on again. Some localities have laws that require the headlamps to be on along with the fog lamps. 3-17