FORD 2004 Expedition v.2 - Manual (Page 216)

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
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. 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 volume. The radio volume may be overridden
using the radio volume control.
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.
2004 Expedition (exd)
Owners Guide (post-2002-fmt)
USA English (fus)
Driving
216