Does anyone know what protocol is used on the diagnostic plug ??

[Chad535]

Considering the small size of code scanners, it must be a simple serial protocol...any ideas ?

[MarkD]

The physical size of the scanner has nothing to do with the protocol complexity. With the processors available now (and in the last few years) a processor with a package sixe of 8 x 8 mm (or less) can have 64KB ( or even more) of flash for code space and 4K bytes of RAM.

[winfred]

i use a snapon mt 2500, the scanner body can be had on ebay for $250-300 the killer is the bmw cartridge/wiring about $500, but it'll do the tranny codes/data and on some of the later cars airbag reset/codes and abs codes. the extra plus most of the other cartridges are cheep on ebay so you can do other cars, you can do obd II bimmers with a domestic car cartridge under generic obd II

[Chad535]

It can't be very complecated with a pair of Rx and Tx pins....RS-232 would have the DTE, DTR, CTS, RTS and some other serial protocols will have more complecated wiring. so maybe it is possible to read the data out using a laptop and some basic converters that convert the signal to RS-232.

[Jochen]

It can't be very complecated with a pair of Rx and Tx pins....RS-232 would have the DTE, DTR, CTS, RTS and some other serial protocols will have more complecated wiring. so maybe it is possible to read the data out using a laptop and some basic converters that convert the signal to RS-232.

Check out www.e34.de (somewhere under "Tips und Tricks") ... yes unfortunately the site is in German but the schematics language is universal ;-) Anyway the only odd thing seems to be the need for 2 serial ports which is a problem with most laptops.

Jochen