Having looked through this forum, it is obvious the fault I have is not uncommon!! Sensors have been playing up for some time now, normally when wet weather, but would start working again when wwather dried out, (even from this it sounds like moisture getting into either the sensor or connectors). Unfortunately they have now been inoperable for several months and I guess it is time to get it sorted. Usual fault indications - constant beep from rear speaker and flashing light on dash switch, regardless whether selected by reverse or switch. Have so far removed each of the rear sensor wiring connectors in turn with no change of symptom; have also isolated all the rear sensors by splitting the connector within the spare wheel bay. Again no change to symptom, and all connections look clean, all wiring looks OK. Control unit looks bone dry - although rear washer doesn't work, have never found any water under the passenger seat (or anywhere else!). After investigating on this forum, have listened to each sensor in turn, and all click. So now my questions! I am guessing this only confirms that the 'send' path is correct, and there could still be a fault with the receive / return (wiring) to the control unit. Which colour wire is the return? (Can't remember what colours I saw, but guess there's a black there for common) Can I isolate front sensors as a bank without removing central trim line of bumper? Can this be done via one of the plugs on the control box, or does the control box 'sense' an open circuit and deem this a fault? Will probably tackle the front section over weekend if it ever stops raining!!