I have been told black and white control boxes are not interchangeable.
with the car in reverse does each sensor give a clicking sound? The one that doesn't if there is one, is the faulty one. All of mine were clicking but I have been having the same problem. yesterday I removed the bumper, pulled the plug and socket apart on each sensor, sprayed with contact cleaner reassembled and disassembled a few times, then took apart and let dry.
Put it all back and it was ok yesterday but only time will tell.
macafee2
i'm talking abut the ecu in the boot but see this
https://www.the75andztclub.co.uk/ind...?thepage=howto there are some pdf files, one is about parking sensors