Codes PO174 and PO171 show up from diagnostic reading
What to do about check engine soon light on 2004 BMW 325i
This is a lin fuel code problems. Check the rubber boot in the intake after the mass air flow sensor'MAF' for cracks, all vaccum hoses allso. Perform a Smoke TEST to be sure there in no Vaccum leaks in the system. There is a hose that connect from the dipstick to the Oil separatoe valve that hot oil will destroid it.
have a smoke test done to determine vac leak to start with. it could be the mass air flow sensor