[Darren69]

A faulty or failing sender unit is usually the cause. Not cheap to replace iirc about £100 from Ducati but there may be cheaper alternatives available. BTW Welcome to Ducati . I have an '02 S4 Foggy which suffers many of the same faults as the basic 01/02 S4. It could of course be something as simple as a dodgy connector or a broken wire so worth going through them all with switch cleaner and multimeter and making sure they're all good connections.