Ford Taurus Owner's Manual page 258

Driving
WARNING: Certain add-on devices such as large trailer hitches,
bike or surfboard racks and any device that may block the
normal detection zone of the RSS system may create false beeps.
The RSS detects obstacles up to six
feet (two meters) from the rear
bumper with a decreased coverage
area at the outer corners of the
bumper, (refer to the figures for
approximate zone coverage areas).
As you move closer to the obstacle,
the rate of the tone increases. When
the obstacle is less than 10 inches
(25.0 cm) away, the tone will sound
continuously. If the RSS detects a
stationary or receding object further
than 10 inches (25.0 cm) from the
side of the vehicle, the tone will
sound for only three seconds. Once
the system detects an object
approaching, the tone will sound
again.
While receiving a warning, the radio volume will be reduced to a
predetermined level. After the warning goes away, the radio will return
to the previous value.
The RSS automatically turns on when the gearshift lever is placed in R
(Reverse) and the ignition is on. An RSS control on the instrument panel
allows the driver to turn the RSS on and off. To turn the RSS off, refer
to Message center in the Instrument cluster chapter for more
information.
Keep the RSS sensors (located on the rear bumper/fascia) free
from snow, ice and large accumulations of dirt (do not clean the
sensors with sharp objects). If the sensors are covered, it will
affect the accuracy of the RSS.
If your vehicle sustains damage to the rear bumper/fascia, leaving
it misaligned or bent, the sensing zone may be altered causing
inaccurate measurement of obstacles or false alarms.
258
2012 Taurus
Owners Guide, 2nd Printing
USA (fus)