Acura 2011 RL Owner's Manual page 384

Backup Sensor System
Within about 24 in (60 cm)
The range of the corner sensors and
the rear center sensors are limited.
Each corner sensor is capable of
sensing an obstacle within about 24
in (60 cm).
378
Within about 59 in (150 cm)
The rear center sensors sense an
obstacle within about 59 in (150 cm).
Do not put any accessories on or
around the sensors.
The system may not function
properly under these conditions:
The sensors are covered with
snow, ice, mud, etc.
When the vehicle is on a rough
road, on grass, or on a hill.
After the vehicle has been sitting
out in hot or cold weather.
When the system is affected by
some electrical equipment or
devices generating an ultrasonic
wave.
When operating the vehicle in bad
weather.