Modern cars are all computer controlled and monitored. Instead of running lots of heavy wires around, smaller signal wires are used, and a small decoder tells things what to do.
The CANbus is the name of the monitoring/signal system
CAN - Car Area Network (You may have neard of LAN and WAN in computer world, Local and Wide area networks)
bus = means signals travel along this route.
When the ISO connector system was created, there is a power plug and a speaker plug, each with eight pins. The speaker works as always.
The power plug would originally have permanent power, switched power, earth, and any or all extras from, aerial output for electric or amplified aerials, lights on to give display dimming, speed input for nav or auto volume control, reverse input for nav systems, telephone mute.
Sometimes car manufacturers have used some of these 'extras' for other purposes.
With CANbus, there is generally only four wires. Permanent power, earth, and the two CANbus signal wires. The OE fit radio has circuitry to decode CANbus signals to know when ignition is on/off, lights, speed, etc. Many are used as teh control centre for many car functions. Aftermarket radios will still be simple original ISO connections.
It is important not to connect the CANbus wires to any aftermarket radio, as any output onto these wires can upset the computer. The correct way to connect such a radio is to use an interface between car and radio. This little box interprets the CANbus signals and provides analogue input to the radio. An alternative is to by-pass the CANbus, remove the wires from the radio connector, and gain a switched feed from another source, often the 12 socket. If lights and speed signals are required, that then gets difficult.
My guess, is that you've connected the CANbus to the radio, and the car body computer has objected, this could be terminal for the body computer if it has not recovered with the radio disconnected.
It now needs to be connected to diagnostic software to see if it has recorded any meaningful failure codes. Generic code readers will not do this, it needs to be Fiat specific, so dealer - expensive, or a program called
MultiECUscan (
MES). There are lots of threads about this program, you'll need to do a search and have a good read.
More inof also here:
http://www.multiecuscan.net/