In the previous article we described the hardware necessary to enable a vehicle OBD system to communicate through the serial port of a PC. As we mentioned you can use a terminal emulator program to read this ASCII coded data or better still try this free Windows program, it not only allows you to talk with the vehicle in a more user-friendly fashion, it also interprets the ‘trouble codes’.Vehicle OBD systems only understand and speak using hexadecimal characters. If you are not equipped with a reference book detailing the OBD protocols it is difficult to make any meaningful communication with an OBD system with just a terminal emulator program to help you. What we need is a user-interface program that converts OBD-2 data into a readable format and likewise converts user commands into OBD-2 messages. It would also be helpful if the program could output a description of the detected fault and suggest possible causes of the problem without the user needing to refer back to a list of codes or the vehicle handbook.