GM Service Manual Online
For 1990-2009 cars only

When it is dark enough outside, the automatic headlamp system will turn on the headlamps at the normal brightness along with other lamps such as the taillamps, sidemarker, parking lamps, roof marker lamps and the instrument panel lights. The radio lights will become more dim when the headlights are off compared to when the headlights are on.

The vehicle has a light sensor located on the top of the instrument panel. Do not cover it or the system may come on whenever the ignition is on.

The system could also turn on the headlamps when driving through a parking garage, heavy overcast weather or a tunnel. This is normal.

There is a delay in the transition between the daytime and nighttime operation of the Daytime Running Lamps (DRL) and the automatic headlamp system 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 the vehicle is started in a dark garage, the automatic headlamp system comes on immediately. Once the vehicle leaves the garage, it takes about one minute for the automatic headlamp system to change to DRL if it is light 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.