Horn
Press 
on the steering wheel pad to sound the horn.
See also:
Reading Lamps
There are reading lamps located on the overhead console and over the rear
passenger doors. These lamps come on automatically when any door is opened.
To manually turn the reading lamps on or off:
...
Overview
A longtime symbol of Cadillac luxury, the DeVille takes on new life as the
DTS for 2006. From its Cadillac-signature exterior styling and luxurious
interior to its powerful, refined ride character ...
Heated Steering Wheel
: Press to turn the heated steering
wheel on or off. A light on the button displays when the feature is turned on.
The steering wheel takes about three minutes to start heating. ...