check the faq.. very first post in the Supra Faq
http://www.toyota-supra.info/forums/...iagnostic.html
this should answer all your questions.
this link is a bit more helpfull in understanding. It basically takes you to the same place as the link supragirl posted in the faq thread. but this is just more direct.
http://www.cygnusx1.net/Supra/TechTi...ror_codes.aspx