mx5cartalk.com

I've found a great resource for OBDII codes.
Not only does it give you the description of the code, it also gives advice on fixing the problem.

http://www.samarins.com/diagnose/codes.html

So they use the same code sequence for all makes and models and year of manufacture

These are the generic codes that will cover most problems you are likely to see, there are other manufacturer specific codes