2008 GMC Envoy Owner's Manual - Page 150

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 are only affected when the light sensor sees a change in lighting lasting longer than the delay. If you start your vehicle in a dark garage, the automatic headlamp system comes on after the transmission is shifted out of PARK (P). Once you leave the garage, it will take about one minute for the automatic headlamp system to change to DRL if it is light outside. During that delay, the instrument panel cluster might not be as bright as usual. Make sure the instrument panel brightness control is in the full bright position. If the vehicle is running and the automatic headlamp system is already on, it can be turned off by turning and releasing the headlamp control at the off position. The automatic headlamp system stays off until you turn and release the headlamp control at the off position again. See Headlamps on page 3-14. Fog Lamps Use the fog lamps for better vision in foggy or misty conditions. The ignition must be in RUN for the fog lamps to work. The fog lamp button is located on the instrument panel to the right of the exterior lamps knob. Press the button to turn the fog lamps on. Press the button again to turn them off. A light glows near the button while the fog lamps are on. Fog lamps turn off whenever the high-beam headlamps are on. Some localities have laws that require the headlamps to be on along with the fog lamps. 3-16