Oil filter housing cap
For two year my car 2008 535i Bmw , check engine light would come on when ever I would stop at a red light or simply let the engine idle. Finally saw an article on YouTube, showing how the oil filter housing may have parts missing. So I ordered a new oil filter housing cap and after comparing the parts found my engines old oil cap was missing the center parts that hold the filter in place and the other part that goes in the center of housing. After I installed new oil filter housing cap the check engine light has not come on.