Hi mate,
Unfortunately there are several things that could be causing it. Rangeing from faulty speedo binacle, to faulty VSS/ abs sensor. The best way to know for sure what is wrong is to have the car put on diagnostic system.
If its a faulty VSS/ abs sensor then they are cheap and fairly easy to replace.
IF the dash is faulty, then cheapest option id to get a second hand dash pod out of another multipla. You will need one that has done less miliage than your current car as the electonic miliage can only be turned forwards and not backwards. Once you fit the new (Second hand) dash pod, the milliage will be falshing. At this point, take it to your local fiat dealer and ask them to carry out miliage correction/proxy alignment and the miliage stored on your multis BCU will be transfered to your new dash and it will stop flashing.
Hope this helps,
Alan
