I had a Mk1 Punto, 1999. I did a lot of searching and couldn't find any proprietary gear to connect, though there was some homebrew stuff, schematics, etc.
There is a three pin connector, right next to the ECU on the offside inner wing. There is some information in Fiat document 07234 General Diagnosis Specification. I quote: "Figure 1 - view of female connector from cable input side". The figure shows a three pin connector with a tab at the lower edge. From left to right, the terminals are marked:
A Line-L (white/blue) UNUSED
B Line-G (black)
C Line-K (white/red)
The document suggests that changeover to the 16-pin OBD type was 1997, but as I say, my 1999 had the three pin connector.
I learned that aside of the electrical connection, the protocol for serial communication is NOT OBD2, though it may be ISO 9141 (with some reference to ISO-5 or ISO-8) or maybe it is ISO-4 (for ECU type IAW16F). That doesn't mean to say that you can't interpret it, but it does mean that no-one out there (as far as I could tell) has written some software to make it easy. The interfaces on e-Bay, etc. are going to be for OBD2 (e.g.VAG-COM KKL interface/lead is common and works with VAG-COM and also FiatECUScan but these are both OBD2 software).
If you are OK with using some sort of hyperterminal to send bytes and capture what comes back, and can produce some interface that copes with different baud rates, you may be able to make some headway. I part chopped my Punto so didn't need to pursue anymore.
Fiat document 07273 Diagnostic Protocol Standard Fiat 9141 discusses the ISO 9141 protocol. This mentions ISO-5 using K-line for bidirectional initialisation and data compared with ISO-8 using K-line for bidirectional data and L-line towards ECU for initialisation only. In both cases, G-line is just ground/earth. It states that ISO-5 shall be used from 1997. Initialisation is at 5 baud, 1 start bit, 7 data bits, 1 odd parity bit, 1 stop bit. You send an address (something to do with system type, I haven't sussed this yet but it's probably somewhere in the document) and the ECU should reply with a 6 byte ISO code at 4800 baud. The bytes have 1 start bit, 8 data bits, 1 stop bit. You'll need to read the document to understand further.
If your ECU is IAW16F, there is a document ref 3.00600, translated from Italian that gives lots of data. That uses ISO 4 which suggests Line-L to send data to ECU and Line-K to receive from ECU. Initialisation is six bytes (OF-AA-CC) at 1200 baud. This must be sent at least 500mS after the ECU sends an ISO code at 1200 baud (this occurs whenever it changes state from power off to power on). After that, communication is at 7812.5 baud with 1 start bit, 8 data bits and 1 stop bit.
Finally,there is another Fiat document that covers the K-line KWP2000 protocol but as far as I know, this is compliant with OBD2 so will not be of use to you. This states that the ECU shall accept 5 baud and also "fast" initialisation. The "fast" rate is 10,400 baud, which is the OBD2 standard. From around 2000, the OBD/OBD2 spec became more standard. Mk2 Puntos have this. Part of that spec is to put the standard 16-pin connector in an accessible position, usually under the dash (Mk2 Punto has it with the fuses on the drivers side, just above the bonnet release).
Some of the documents I have referred to can be found on the forum of FiatECUScan.net. I think the IAW16F doc is posted elsewhere on the net.
If you are searching the net, check out groups for Alfa and Lancia as well as these are from the same stables.
red
