Cadillac 2007 DTS Owner's Manual page 208

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.
208
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.