Automobile IO

SAE standard J1850 is available for $63 from http://www.sae.org/technical/standards/J1850_200606 "This SAE Standard establishes the requirements for a Class B Data Communication Network Interface applicable to all on and off- road land based vehicles. "

ISO9141/2 is available for $28 at http://www.sae.org/products/standards/ISO9141_2.htm "This part of ISO 9141 describes a subset of ISO 9141:1989. It specifies the requirements for setting up the interchange of digital information between on-board emission-related Electronic Control Units (ECUs) of road vehicles and the SAE OBD II scan tool as specified in SAE J1978."

But as http://www.northstarlabs.com/rp6.htm notes, there is significant divergence in the implementation of the physical layer used by auto mfgrs between SAE J1850 and ISO-9141

http://www.obd-ii.com/ is the ODB-II home page "Dedicated to helping the home and independent technician understand and use OBD-II technology." Well... actually they sell a $250 PC-Auto interface. They do list the DTC codes (cached 20010220135132) however.