Warning: Even with a PPS, you need to be especially careful when reversing. It should be remembered that in bad weather conditions, for example, in heavy rain or snow, the PPS may not always give accurate results.
The PPS is switched on automatically, simultaneously with the engagement of the reverse gear. Its operation is indicated by the flashing of all three lights and a sound signal. How the system determines the distance and signals about it is shown in the illustrations.
If the PPS fails to operate, for example, if the sensor is faulty or there is interference from an external sound source, all signal lamps will go out, leaving only the sound signal.
Warning: The sensors should never be covered with dirt, snow or ice. However, do not use sharp objects to clean them.
Driving with a trailer can also cause inaccuracies in the system"s operation.
(The original text is provided on an online resource: FORDBOOK.ru)