Cadillac 2007 Escalade EXT Owner's Manual page 216

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The ultrasonic sensors are not kept clean. So,
be sure to keep your vehicle's rear bumper free
of mud, dirt, snow, ice, and slush. For cleaning
instructions, see Washing Your Vehicle on
page 501. If the DIC still displays the PARKING
ASSIST OFF message after cleaning the
bumper and driving forward at a speed of at
least 15 mph (25 km/h), see your dealer.
•
Other conditions that may affect system
performance include vibrations from a
jackhammer or the compression of air brakes
on a very large truck or other mechanical
devices that interfere with URPA performance.
•
When URPA is disabled without driver action
and the driver attempts to turn URPA back
on by pressing the rear park aid button, the
indicator light will flash for 3 seconds and then
stay lit to indicate that URPA is off.
216
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.
For Driver Information Center messages related
to URPA, see DIC Warnings and Messages
on page 248.
If the vehicle bumper is damaged, the URPA
system may not work properly. Take the vehicle to
your dealer to repair the system.