Firstly we need to know what your car is.

If you have a 525i/530/535/540/M5 then you don't need a code plug for the OBC as it uses the one in the instrument cluster.

If you have 518/520/524/525tds then you will need a different OBC to the one that you have. I've never seen one of these but they would have a connector on the back that would be for the code plug.