BMW reports that owners of X3 model SUVs and 3-Series sedans and wagons (all with N47T diesel engines) may complain of a rattling sound underneath the front of the vehicle when the engine is idling.
One likely source of the noise, says the carmaker, is a loose band clamp that retains the diesel particulate filter to the front exhaust pipe (see illustration).
A redesigned band clamp that holds its retention better and longer is now available to address the condition. Check with a dealer for the specific part number of the clamp in question.