One problem related to emission control has been reported for the 2004 BMW 530. The most recently reported issues are listed below.
This 2004 BMW 545i car has a problem which causes emissions warning light to come on frequently and the subsequent fuel mileage to be reduced in half. The dealership is unable to permanently fix the problem -each attempt to fix the problem lasts for only about one month. It as been to the dealer approximately 8 times for this condition and is clearly harming the environment. I have also been in contact with the regional office and they are of no help.