There is a 3 pin connector in the engine bay that is used for reading the error codes. To use this you can make yourself a reader. e.g. a simple LED reader http://www.fordscorpio.co.uk/star.htm or more complicated text display reader http://homepage.ntlworld.com/a.harby2/ggpfcrpg.html Commercial stuff ranges from simple LED readers e.g. http://www.drapertools-online.com/b2...pp_skmno=68082 up to more expensive stuff like the Syke Pickavant ACR2 and upwards.