A standard in the US established in 1996 specifying standard methods for accessing vehicle engine computers, emissions controls and various other stuff. Someone should edit this with a better explanation.

A standard in the US established in 1996 specifying standard methods for accessing vehicle engine computers, emissions controls and various other stuff. Since the 1996 model year, North American automobiles have been required to provide an OBD (On Board Diagnostics) data port for the connection of test equipment. This port is used to obtain emissions-related diagnostics information, and in some cases can also be used to obtain real-time vehicle operating parameters.

In Europe this standard was adapted and called EOBD. Since 2001 gasonline engines and since 2003 diesel engines are required to be EOBD conform. Honda EDM ECUs from 1996-2000 use a 3-pin plug (that is not OBD-compatible) for communication to diagnostic equippment.