In last month’s article we took a look at the background and specification of the OBD-2 diagnostic connector fitted to new cars. Now, as promised we present an interface adapter that allows your car to confess its innermost secrets to your computer.We can thank an EU directive dating from 1998 for the introduction and standardisation of the OBD-2 vehicle diagnostic connector. The connector is standard on all spark-ignition engined vehicles from 2000 and should be fitted to diesel engined variants by 2003. The communication protocols used can come in three different varieties. In Europe the most common protocol is the ISO standard. All of these protocols rely on serial data transfer but the signal levels and message format are not compatible with the serial communications port of a Personal Computer.