Rear parking sensor problem

[Johnbmwz4]

Hi , after the ear to the parking sensor test it looks like one of my sensors has failed. Was hoping to be able to reach up from underneath and replace it but not a chance so it looks like rear bumper off time which I'm not looking forward to. Is it an easy job and is there any links to how it's done?
Thanks

 

[owm]

You have to remove the rear bumper but it seems easy enough:
http://www.z4-forum.com/forum/viewtopic.php?f=3&t=40568

 

[Johnbmwz4]

Read a post on here saying that it is possible to access them by taking out one of the rear lights so I will try this at the weekend weather pending.