Thanks Andrew, they are the same yes, and I have considered awapping them, a little weary purely because the bolts and brackets to the sensors are a little tired, as was the case of the faulty RH sensor and don't want to kill a tired but functioning sensor. It its certainly worth a bit more thought, oddly, I have juat been out to collect my daughter and its currently clear and staying clear, sort of pointing as you suggest to a connection issue. I know that the sensor end of the loom on the L322 range rovers that share the same platform as our e53s suffer from cable failure and a section of loom and plug us available as a repair kit. I guess as they are so similar in design, it's logical to assume it could well be the case with the x5s. Will report back, when I have something to update the thread with.