Ford 2010 Transit Connect Owner's Manual page 173

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
6 feet (1.8 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.
The RSS automatically turns on
when the gearshift lever is placed in
R (Reverse) and the ignition is on.
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.
172
2010 Transit Connect (tst)
Owners Guide, 3rd Printing
USA (fus)