Oldsmobile 2004 Silhouette Owner's Manual page 182

If an object is detected at a REVERSE (R) speed of
less than 3 mph (5 km/h), one of the following will occur:
Description
amber light
amber/amber lights
amber/amber/red lights
& continuous chime
amber/amber/red
lights flashing &
continuous chime
A chime will sound the first time an object is detected
between 20 inches (0.5 m) and 5 feet (1.5 m) away.
URPA cannot detect objects that are above liftgate level.
In order for the rear sensors to recognize an object, it
must be within detection range behind the vehicle.
3-26
English Metric
5 ft. 1.5 m
40 in. 1.0 m
20 in. 0.5 m
1 ft 0.3 m
When the System Does Not Seem to Work
Properly
The light may flash red when the vehicle is in
REVERSE (R) if the ultrasonic sensors are not kept
clean. So be sure to keep your rear bumper free of mud,
dirt, snow, ice and slush. Other conditions that may affect
system performance include things like the vibrations
from a jackhammer or the compression of air brakes on a
very large truck. If after cleaning the rear bumper and
then driving forward at least 15 mph (25 km/h), the
display continues to flash red, see your dealer.
If a trailer was attached to your vehicle, or a bicycle or
an object was on the back of, or hanging out of your
liftgate during your last drive cycle, the light may
also flash red. The light will continue to flash whenever
in REVERSE (R) until your vehicle is driven forward
at least 15 mph (25 km/h) without any obstructions
behind the vehicle.
For cleaning instructions, see Cleaning the Outside
of Your Vehicle on page 5-95 .