GMC 2011 Sierra Owner's Manual page 370

There are three ways to end cruise
control:
To disengage cruise control;
step lightly on the brake pedal.
Press on the steering wheel.
To turn off the cruise control,
press on the steering wheel.
The cruise control set speed is
erased from memory by pressing
the button or if the ignition is
turned off.
For vehicles with the Ultrasonic
Rear Parking Assist (URPA) system,
it operates at speeds less than
8 km/h (5 mph), and assists the
driver with parking and avoiding
objects while in R (Reverse).
The sensors on the rear bumper
are used to detect the distance to
an object up to 2.5 m (8 ft) behind
the vehicle, and at least 25.4 cm
(10 in) off the ground.
The Ultrasonic Rear Parking
Assist (URPA) system does not
replace driver vision. It cannot
detect:
Objects that are below the
bumper, underneath the
vehicle, or too close or far
from the vehicle.
Children, pedestrians,
bicyclists, or pets.
If you do not use proper care
before and while backing, vehicle
damage, injury, or death could
occur. Even with URPA, always
check behind the vehicle before
backing up. While backing, be
sure to look for objects and check
the vehicle's mirrors.