sensor fault warning light has come on, not beeping in cab.
external warning beeper working ok.
have checked connections to sensors, all seem ok.
any ideas? before i take it in for a diagnostics.

Are they factory ft sensors?

yes, factory fitted.

update on my problem... listened to each sensor whilst in reverse, all but one clicking (obviously faulty one). quote from fiat £97.50+vat for one sensor(ouch). quote from bosch parts supplier £157including vat for one sensor (even bigger ouch). can get complete new kit (same make/model) for £155including vat, on-line, which means i have spares and can just plug new sensor in (still an ouch, but seems best way of doing it).:

Did you check by swapping sensors that its actually the sensor and not wiring, control unit etc? SAme sensor on doblo, bravo and near identical ones on some fords, citroens I'd be surprised if you couldn'r source one to work in your local scrappie.

yes, tried swapping sensors around, have contacted scrappie's, no joy yet. thanks.

I'd be buying a complete vebra set with display (or similar) from ebay for £15.