It's a LOT more complicated then just wiring a serial connector to one end. This link offers a kit where you can make your own adapter, or you can buy one premade.
hi! is there some link or something where i could find RS232-OBD2 or USB-OBD2 cable schematics for VW Passat,1997 ?
thanks!!! o, is it possible to reprogramm ECU without pulling it out on this car model?
"All" ECUs are reprogrammable without being uninstalled. You will need a reflasher hardware / software and availability to the flash binary files. Well beyond hobbyist budget but every day in every dealership. The methods to flash a vehicle are becoming more standard, but until now, all vehicles are flashed in an OEM proprietary method. The normalized method is called "Pass thru reprogramming".