We have a 2012 pop 1.4 multyair. i installed a pioneer radio and now the KM display flashes. The one you shows total distance traveled. I am sure the problem is the small white 6 0r 8 pin connector was hooked up to the original radio. Does anyone has a pin print out on this connector or does anyone know what this one is for? Or how I can make the flashing stop, it is distracting.
THX

Disconnect the radio before you do any expensive damage.

Your car, presumably a 500, is controlled by CANbus. Instead of lots of wires, there are two tiny wires which carry signals, interpreted by the receiving unit.

The original radio plug carries a live feed, an earth, and the two CANbus wires. Despite the change to the wiring, Fiat, and most others, have continued to use the same plug. CANbus must not be connected to aftermarket radios directly. Usually an adaptor is used, that interprets the CANbus signals and feeds the radio analogue signals.
http://www.connects2.co.uk/products/can-bus-adapters/universal

The km display flashing is an indicator that one or more CANbus nodes, almost certainly the radio, is not communicating properly. You do not want to be putting 12v up the CANbus wires.

Hi,
Welcome to Fiat Forum.
Assuming you havee not connected the cars CAN bus to the new radio you need to perform a "Proxi-Alignment" to reconfigure the car without the original radio. If you want any steering wheel controls etc to work with the new radio you will probably need a converter unless the radio is designed for Fiat's. You will still need the Proxi-Alignment.
This needs Fiat specific diagnotic software either a Fiat Dealer/specialist or you can DIY with Multiecuscan www.multiecuscan.net , ELM327 interface and adaptor leads.

Robert G8RPI.