Cadillac 2006 DTS Owner's Manual page 178

Sensors
The solar sensor, located in the defrost grille, middle of
the instrument panel, monitors the solar radiation.
Do not cover the solar sensor or the system will not
work properly.
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There is also an interior temperature sensor located
next to the steering wheel that measures the
temperature of the air inside your vehicle.
There is also an exterior temperature sensor located
behind the front grille. This sensor reads the outside air
temperature and helps maintain the temperature inside
the vehicle. Any cover on the front of the vehicle could
cause a false reading in the displayed temperature.