Just got a 2009 550i M Sport from a guy that didn't want to fix the car so I got it for a great price. I wanted to ask this,,,,the guy said he thinks it's the gas cap that is puttin up a p0325 code but I know it's the knock sensor code. Would a bad gas cap cause that code, i know if the car gets low on fuel the light comes on but if I fill it up it's goes away I also am looking a putin new upper and lower control arms on, what brand do u guys recommend to replace them with?

 

Don't know about the gas cap, never heard of that before.

For the control arms, use the OEM ones you can get these from Euro car parts or from Car parts 4 less, who are the online suppliers and cheaper. Go for the Lemforder ones, these are the ones that came on the car from factory. OEM control arms contain hydrolic fluid which is used when the car is going at speeds to tighten up the suspension. The aftermarket ones don't give the same, they are all rubber, which wear over time.

Hope this helps!