1 Answer

Vacuum leak 

Code PO171- Lean mix of Bank 1 (passenger side of engine)
Code PO174- Lean mix of Bank 2 (driver's side of engine)

Most of the time a P0171 and P0174 is caused by either a vacuum leak--more than likely the PCV hose and valve or a dirty or defective MassAirFlow sensor. Low fuel pressure can also cause this condition. The PCV hose is located on bank one but can affect both sides because the other end is located on the back of the upper intake manifold. Usually they deteriorate and get a hole in it.

So listen under the hood, with the car running, for a hissing noise. if you have one of these, then you have a vacuum leak and need to replace the hose. if not you might still have a small hole, but can't hear it yet. http://answers.yahoo.com/question/index?qid=20090730050746AAifK5x