The code on my car read p0171, bank 1 too lean. I changed the oxygen sensor, the mass air flow sensor is good, and there are no vacuum leaks. What else could it possibly be? I can't get the code to go away. It keeps popping up after I look for a problem and fix a problem and clear the code it keeps coming back. I don't know anything about cars and the people that are helping me can't figure it out either. I have a 2001 Toyota corolla ce sedan.