FORD 2003 Expedition v.2 - Manual (Page 224)

The RSS detects obstacles up to
2 meters (6 ft.) 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 25.0 cm
(10 in.) away, the tone will sound
continuously. If the RSS detects a
stationary or receding object further
than 25.0 cm (10 in.) 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.
Whenever a warning is received, the
radio volume will be lowered to a
volume that will allow the tones to
be heard. The radio volume will return to the previous level after the
warning goes away.
The system is automatically enabled when the gear selector is placed in
R (Reverse) and the ignition is ON. The RSS control in the message
center allows the driver to disable the system only when the ignition is
ON and the gear selector in R (Reverse).
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.
CONTROL TRAC FOUR-WHEEL DRIVE (4X4) OPERATION
(IF EQUIPPED)
For important information regarding safe operation of this type
of vehicle, see Preparing to drive your vehicle in this chapter.
Driving
224