Cadillac 2011 DTS Owner's Manual page 130

See Towing a Trailer on page 5 26 for more
information.
This position is also used for normal driving.
However, it reduces vehicle speed more than D (Drive)
without using the brakes. You might choose 3 (Third)
instead of D (Drive) when driving on hilly, winding roads,
when towing a trailer, so there is less shifting between
gears and when going down a steep hill.
This position reduces vehicle speed more
than 3 (Third) without using the brakes. You can use
2 (Second) on hills. It can help control vehicle speed as
you go down steep mountain roads, but then you would
also want to use the brakes off and on.
This position reduces vehicle speed even
more than 2 (Second) without using the brakes. You can
use it on very steep hills, or in deep snow or mud. If the
shift lever is put in 1 (First) while the vehicle is moving
forward, the transmission will not shift into first gear until
the vehicle is going slowly enough.
3-28
If the vehicle has this feature, it can detect a change in
driving patterns. If you make an aggressive driving
maneuver, the vehicle's transmission automatically
shifts to the lowest possible gear to maximize vehicle
performance. The vehicle will automatically return to
normal operation when you return to normal driving
patterns.
To set the parking brake, hold the regular brake pedal
down, then push the parking brake pedal down.
If the ignition is on, the brake system warning light on
the instrument panel cluster should come on. If it does
not, you need to have the vehicle serviced.
The parking brake pedal
is located to the left of the
regular brake pedal, near
the driver door.