Ford F-150 2010 Owner's Manual page 298

Driving
The RSS detects obstacles up to
6 feet (2 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 may be reduced to a
predetermined level. After the
warning goes away, the radio will return to the previous volume.
The RSS may have reduced performance or an increased chance of false
detection if the tailgate is not locked and in the upright position. If the
tailgate is down, the RSS tone may be heard intermittently or
continuously. The tone may also be heard if items in the truck bed
protrude rearward outside the bed.
The RSS automatically turns on when the gearshift lever is placed in R
(Reverse) and the ignition is on. A control in the message center allows
the driver to disable the system, refer to Message center and Rear park
aid in the Instrument Cluster chapter for more information.
Note: If the system cannot be turned off, refer to MyKey™ in the Locks
and Security 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.
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