Hi,

I'm gathering some information about how to build my own diagnostic fault interface (=hardware) running with some free or demo software...

what I found out until now:

the data link to access e.g. the airbag control unit is based on iso9141, which can have an K and and L data link wire, but on most cars (and actually, as far as I know, on Fiat) only the K- wire is used (I could be mistaken there). Data rates are typically under 10 kbit/s, Fiat seems to use 4800 baud, at least for the interface to its airbag control units:

Fiat Brava 46413633
Fiat Brava 46538652 5WK42819 Siemens
Fiat Brava 46541774 Breed 5WK42811 Siemens
Fiat Brava 46541775 Breed 5WK42816 Siemens
Fiat Bravo 464793640
Fiat Bravo 46550647 TRW
Fiat Bravo 46768868
Fiat Bravo 46768869 5WK42816

iso9141 is basically a serial protocol which is easy to implement using any old computer featuring a RS232 interface.

there is quite a lot of information on iso9141 hardware on the net:

driver IC

Iso K-Line serial interface

I wonder if any information on parts-specific fault codes and fault code adresses is available on the net... but these would not be needed it the interface runs with standart software. What the interface actually does is just to shift and adapt voltage levels between PC and car electronics... so any standard software should run, or am I mistaken?

bye the way, I also found some other post in the fiat forum, will give it a read...

Edit: the ECU for my Bravo (1.4 12V) would be a Monomotronic MA 1.7.3 which seems not to be OBD-2 compliant.

check this out... (bablefish translation of german web page)

there is no free or demo software out there to do this.. if you can program with hardware interfaces and serial ports then feel free to try.

you're correct L line isnt needed (hence only 3 pins on the fiat connectors, K line, chassis ground and chassis signal).

the interface is very easy to build, just copy the elm electronics ELM323 design for the ISO232 to ODB interface.

fault code info is easily found online, including fiat specific codes.

you can get cracked versions of uniscan online, they can use ISO9141.

reddy4bed (tony) has made his own software. you could ask him nicely if he will give you a copy.

I'm going to give it a thorough testing with an XP conversion and see if it works sometime this week, and then anyone can have it.

give it a pretty GUI and start selling it on ebay complete with an interface for £75, i bet you'd sell a few dozen.

I cant make pretty GUI's mine are ugly!.