E53 2001 Rear parking sensor problem

[Paul S]

Hi All
I have an E53 2001 with a problem with the parking sensor.
When you put it in reverse the sensor light is full on in the car. The sensors give the normal beep when near an object, then after a few seconds gives a continuous beep even when there isn't an object that close to the rear of the car. (The front sensors are fine). I have cleaned them also listened to them close up to check they are individually 'clicking' and they all are - and all 'clicking' at the same rate.
If the car is turned off then the next time it is put in reverse, sometimes it repeats this process, other times it just gives the continuous beep.
Today I located the sensor box next the the battery, unplugged the 3 plugs, no signs of problems, then refitted. This has made the problem more intermittent but not solved it.
I would welcome any suggestions please - thanks you!