You won't regret it, if you ever have a FIAT or Alfa Romeo (or Lancia) to look after in the future...
To clear up a small point mentioned earlier: ELM327 is the newer-style interface required for the FIAT 500, Grande Punto, Panda, etc. - basically everything of the Stilo's age and newer - because it is capable of connecting to the body computer or the instrument panel, that is what I meant when I said it was required for the 500 (I assumed we were still talking about resetting the service interval).
KKL (VAG-COM-type cable), often translucent blue, is useful mostly for pre-CAN bus vehicles older than a Stilo. Each ECU tends to have its own pin in the FIAT/Alfa connector, but the KKL cable has only pin 7 connected. Therefore, it is necessary to bridge pin 7 to various other pins (1, 3, 9... etc.) to connect to various ECUs.
Typically, people modify the plug, as the pins are easily accessed and soldered to. The danger is that plugging such a bridged cable (specifically with a bridge from pin 1 to pin 9) into a newer-type vehicle (500, Panda, etc.) will short out the CAN bus, which may cause confusion and damage. Note that Most Easterly Pandas probably has an un-modified KKL cable or at least a KKL cable without a bridge to pin 9. This point is explained in red text on the 'Supported vehicles' page (
http://www.multiecuscan.net/SupportedVehiclesList.aspx)
It's true that the KKL cable will work with the 500 for some functions, but the ELM327 cable will work for all functions.
I also find that the ELM327 is more reliable because it has its own signal timing generator, where the KKL cable is affected by the latency of USB ports - on laptops, these can be quite dodgy. For the record, FIATECUSCAN with KKL wouldn't work at all for me on a Sempron Compaq/HP laptop or my ASUS Eee PC, but worked fine once I had a 'full strength' HP laptop with i7 processor.
There are three possible adapter cables required in addition to the ELM327, which can be made up by wiring together plugs and sockets as shown on the right-hand side of the 'Compatible Vehicles' list. Note that Adapter 1 bridges 1, 7, 9, and 12, and therefore can't be used on the 500, Grande Punto, Panda etc.
To make the adapters, I find that wrecked Alfa 156s are a good source of OBD sockets, as the 156 socket is on flying leads rather than integrated into the fusebox. I suppose it is faintly ridiculous that three 156s have to die to furnish one's toolbox with a complete set of adapters... Plugs can be bought easily. Perhaps I can find new sockets somewhere too.
EDIT: Well, this is by far the easiest way - costs about the same as ONE plug bought locally... and you get all three adapters, with colour-coding for easy recognition (open Gendan style ): http://www.gendan.co.uk/product_FESCBL.html
I think it speaks volumes that Gendan - a leader in diagnostic gear - is selling
MultiECUScan.
Anyway, to be safe, I start with my 'new' ELM327 cable first, which is useful even on older vehicles for engine and transmission ECUs. I use the KKL cable for other older applications, such as airbag ECUs (pin 3). The software simply won't allow you to use the ELM327 for some older applications, nor will it use the KKL for many newer applications.
I also think it is better to make up adapter cables, rather than modify the plug, because then you can be certain that you are plugging an un-bridged cable into the newer cars (avoiding the risk mentioned above). Alexh365's method of using a switch is good too except for two hazards: (i) the switch has to be positioned carefully, or it will impede the fitting of the plug into some of the more deep-set sockets out there. (ii) you would have to be very certain that the switch position was correct before plugging into the car. For the technician in a hurry it is probably easier to identify the adapter cable, rather than the switch position.
Have fun! It's very helpful being able to get your car to share its feelings...
-Alex
