diagnostic port question ......

[fsteyer]

on my '95 E34 I have a round diagnostic port. When I take off the cap, there is a circuit board with pins inside the cap. What does the board and pins do?

Thanks .......

[shogun]

http://www.europeantransmissions.com/Bulletin/bmw_pin_layout_20_plug_connector.htm
http://www.wikitt.org/wikiTT/index.php?title=OBD
http://www.scribd.com/doc/1703639/BMW-ERROR-CODES