Cadillac ESCALADE EXT 2002 Manual page 192

If the URPA Display Flashes Red
If the URPA system is not functioning properly, the
display will flash red, indicating that there is a problem.
The light will also flash red while driving if any of the
following conditions exist:
D
-
A trailer or trailer hitch ball mount is attached to
your vehicle.
D
A bicycle or object is on the back of, or hanging out
the cargo area.
D
If the tailgate is lowered.
D
If your vehicle is moving in REVERSE (R) at a
speed greater than 3 mph (5 km/h).
The light will continue to flash until the trailer or the
object is removed or the tailgate raised and your vehicle
is driven forward at least 15 mph (25 km/h).
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It may also flash red if the ultrasonic sensors are not
kept clean.
So be sure to keep your rear bumper free of mud, dirt,
snow, ice and slush or materials such as paint or the
system may not work properly. If after cleaning the rear
bumper and driving forward at least 15 mph (25 km/h),
the display continues to flash red, see your dealer. For
cleaning instructions, see "Cleaning Your Vehicle" in
the Index.
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.
As always, drivers should use care when backing up a
vehicle. Always look behind you, being sure to check
for other vehicles, obstructions and blind spots.