Used Ulysse help needed

Hi,
I'm looking to buy a used Ulysse and have found an 03, 53 plate Eleganza which I like the look of. Taken it out for a test drive and everything seemed fine apart from a constant beeping noise from the back. When I first got in, I had to reverse out of the garage space and the beep started and changed pitch, so I presumed that the rear parking sensors were working fine. Unfortunately, the beeping then continued for the duration of the test drive (about 10 minutes). The dealer says that he replaced a sensor when he first got the car ashe'd had the same problem, but that that had fixed it.
What do you guys think? Dodgy sensor or something more serious? I can't drive a car with constant beeping and don't want to buy one where to solve that problem might cost a lot.
Any help/advice gratefully received!

Hi there, i have this model and a similar beeping noise occassionally occurs - i think it is to alert a fault/warning and sometimes i think it's linked to the non wearing of seatbealt and doors. We find if it starts and drive for a few miles, stop, get out, lock up and then unlock, get in, put on seat belts etc it has gone. But our Fiat dealer in Belfast had not a clue! In saying all of this we now have an exhaust noise from the top-rear of the engine and having difficulty having it diagnosed other than one garage suggesting it's the injectors that will cost an arm and two legs to repair so beware.

To rest the beeping noise I think you press and hold the dark button on the RT3 unit (ICE) until the systme resets itself. Mine does it as well but it's pretty infrequent and now I know how to deal with it it isn't a problem any longer. Don't expect a dealer to sort it out, they haven't a clue!

this cure was posted nearly 2 years ago....by a dealer

WellI eventually bought it even with the beep! Have tried the dark button, but this only resets the RT3 system, not the parking sensors. As soon as I put the car into reverse, the beeping starts and doesn't stop until about 5 minutes after the engine is stopped - no matter how far I've driven in the meantime forwards!
Any other suggestions?