Hey Frakster...I've attached a link to our E90 tech articles that I think you'll find helpful in troubleshooting your issue. If you have any further questions, don't hesitate to post a Comment just below the article and someone will get back to you with more detailed info. Hope this helps and best of luck!
BMW 3-Series E90 (2006-2013) Technical Articles - Pelican Parts
-Dmitry