Thanks.The diagnostic system has to be readable by all, for the powertrain. The rest of the vehicle can be manufacturer specific. Fiat especially seems to talk an alien language for most diagnostic systems, so unless the garage has Fiat specific software, they may not see stored faults for non-engine systems.
Lots of us on here use an aftermarket diagnosis system designed for Fiat Group vehicles, called MultiECUscan (MES). There is a thread specifically to show those with the software ready to help others. https://www.fiatforum.com/directory/categories/multiecuscan-register.4/
Knowing where you are might help. This is why the forum has a location option.
Ideally, the car needs its codes read, to identify any that might be stored and applicable. A Fiat dealer will charge an hour labour to do this, forum members tend to charge by the mug of tea.
I'm Barnsley South Yorkshire so I'll have to see if there's.anyone near me and also if I feel.safe getting it there, currently just doing the small journeys. With it showing a fault somewhere and tending to cause larger issues, its knocked my trust in it, don't want it going into limp mode and me being miles from home.