Ford 2003 Excursion Owner's Manual page 135

To help avoid personal injury, always use caution when in R
(Reverse) and when using the RSS.
This system is not designed to prevent contact with small or
moving objects. The system is designed to provide a warning to
assist the driver in detecting large stationary objects to avoid damaging
the vehicle. The system may not detect smaller objects, particularly
those close to the ground.
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.
The RSS automatically turns on
when the gear selector 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,
the ignition must be ON, and the
gear selector in R (Reverse). An
Driving
OFF
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