I've not seen any independently published data other than the Haynes AutoFix online manual . All the Fiat info is now basically online and restricted to dealers and VAT registered garages and expensive.
I have the Haynes AutoFix for my specific 500X and it is fairly good and does have some wiring diagrams.
For the money the Haynes is good value compared to Fiat dealer eLEARN and whilst original content was rather lacking they do add move over time.