The round 20 pin BMW diagnostic port is the only one you can access on your car. OBD2 ports (the 16 pin D shaped ones normally found under the dash on the driver's side) were not fitted until MY2000. Your best option would be to install some diagnostic software on a laptop and get an ADS/OBD interface from someone like http://interfaces4beemers.com/
, which will allow you to read codes from all modules in your car. If you just want to check and clear engine-related codes, get a Peake R5/FCX3 tool.
For US cars, you can use the stomp test to read the diagnostic codes - you can find instructions here http://www.pelicanparts.com/BMW/tech...de_Reading.htm