Volvo 2008 S40 Owner's Manual page 152

NOTE
Front park assist is disengaged automatically when the parking brake is applied.
If the vehicle is equipped with front and rear park assist, both systems will be deactivated by pressing the button.
Audible signals from the park assist system
The Park Assist system uses an intermittent tone that pulses faster as you come close to an object, and becomes
constant when you are within approximately 1 ft (30 cm) of an object in front of or behind the vehicle. If the volume
of another source from the audio system is high, this will be automatically lowered.
If there are objects within this distance both behind and in front of the vehicle, the signal alternates between front and
rear speakers.
Faults in the system
If the information symbol illuminates and
display, this indicates that the system is not functioning properly and has been disengaged. Consult a trained and
qualified Volvo service technician.
CAUTION
In certain circumstances, the park assist system may give unexpected warning signals that can be caused by external
sound sources that use the same ultrasound frequencies as the system. This may include such things as the horns of
other vehicles, wet tires on asphalt, pneumatic brakes, motorcycle exhaust pipes, etc. This does not indicate a fault in
the system.
164
06 Starting and driving
Park assist (option/accessory)
Cleaning the sensors
The sensors must be cleaned regularly to ensure that they work properly. Clean them with water and a suitable car
washing detergent.
NOTE
PARK ASSIST SERVICE REQUIRED is shown on the information