2005 530i

Driving home today check engine light comes on so I go have code read they said engine running to lean?? Any answers as to why? Would it be an O2 censor or maybe need to change fuel filter? Cleaned the max air flow sensor still no change...

im guessing it was P0171 System too lean (Bank 1)? First thing i would do is look for a vacume leak. You can do this by spraying carburetor cleaner around your vacume lines, any increase in RPM would indicae a vac leak. There are other possible causes but this is a good place to start. Is the car running rough? Did they clear the codes after reading them?

Thanks for the reply I'll definantly start there this weekend!!