Oh and if you go here you can read what each code means. Click on BMW in this case. Also click on codes explained, it will tell you about the most important digit in the code, position 3. In your case speed/idle control (number 5). It will take the myth out of the codes for you.

http://www.obd-codes.com/trouble_codes/index.php


If you want to get more into diagnosis pick up the OBDll Bible by Peter David and Bosch fuel injection and engine management by Charles Probst. Obviously not for everyone, but to learn the fundamentals these are great books.