visually check the sensors for anything blocking them, or else, you might have a short. a technician will find out the faulty one or the short circuit, they are not that hard to get out of the bumper (attached via clips on E53)

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BMW X5 3.0si 2008
Premium Package
Light Package
Navigation
Reverse Camera
Rear Sensor (retro-fit)
Comfort Access
Spare Wheel
Power folding mirrors
Voice Control w Bluetooth
Power trunklid

BMW X3 3.0i 2006
M Aerokit
M Sport Package
Navigation System
BT Handsfree
Xenon HID

BMW X5 3.0i 2001 --- SOLD