This Fiat 500 was dropped off to us by a local dealership as the factory radio had gone bad. The dealership had verified that the bluetooth module and radio module were both defective and it would cost too much to replace. These newer cars run data to turn on the radio and we confirmed that no power was going to the head unit whatsoever. This meant that we had to run our own custom wiring to power the new head unit.
We used a Metra dash kit that was perfectly matched with the factory plastics. The factory deck was pretty worn out after 100,000 kms of use and putting in this new head unit and dash kit made the interior feel a lot newer. Installation-wise, a smaller mechless receiver will be a lot easier to install as space behind the factory radio is limited. Metra's instructions stated that modification to the dash may be required but we had no issues with the Pioneer MVH-S312BT mechless single din.
The Fiat dealer did instruct the dealership that dropped off this car that the odometer may flash the mileage if the stock radio is removed. However, as the factory radio had died it was doing this already. It may be possible to code this out by the dealership but it's worth noting their hourly service rate if you choose to do so. Metra does make a data interface, the XSVI-6515-NAV that can be used to retain all the factory inputs, amplifiers, and provide NAV outputs. We did not use that module in this case as steering controls were not needed and this car did not have a factory amplifier. The Pioneer deck has its own USB port, auxiliary input, and handsfree mic so none of the factory components needed to be retained. This budget-minded radio still offers the same great reliability and sound quality Pioneer is known for.