Hi guys, now got park assist fixed. I watched a video on u tube where the guy put his finger on each sensor and if they ticked they were OK, also another one who went round them with his phone and recorded the ticking noise which meant they were OK. I tried both methods and by their reckoning they should have been A OK but they still did not work. I removed the rear bumper and took the 4 sensors out and tested the resistance with a multi meter and got a zero reading from all 4. I replaced them with 4 new ones and hey presto park assist has returned. cheers Paneuro P.S. I forgot I also tried a guaranteed fix from a prominent BMW techy which was spray them with WD40 and that was just a waste of WD40.