Automatic Headlamp System
When the exterior lamp control is set to AUTO and it is dark enough outside, the headlamps come on automatically.
There is a light sensor located on top of the instrument panel. Do not cover the sensor; otherwise the headlamps will come on when they are not needed.
The system may also turn on the headlamps when driving through a parking garage or tunnel.
When it is bright enough outside, the headlamps will turn off or may change to Daytime Running Lamps (DRL).
The automatic headlamp system
turns off when the exterior lamp
control is turned to 
or the
ignition
is off.
See also:
Service Publications Ordering
Information
Service Manuals
Service Manuals have the diagnosis and repair
information on engines, transmission, axle suspension,
brakes, electrical, steering, body, etc.
Service Bulletins
Service Bulletins ...
OnStar®
If the vehicle is equipped with an
active OnStar system, that system
may also record data in crash or
near crash-like situations. The
OnStar Terms and Conditions
provides information on data ...
Potential Issues
Some OnStar services are disabled
after five days. OnStar cannot
perform Remote Door Unlock or
Stolen Vehicle Assistance after the
vehicle has been off continuously
for five days. After five ...