DTCs P0171 and P0174 System Too Lean Diagnostic Aids
WARNING: This page does not describe the selected car, but rather 16 other vehicles, including the 2011 Mercury Mariner, 2011 Lincoln Navigator L, 2011 Lincoln Navigator, 2011 Lincoln MKX, and 2011 Lincoln MKT. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:
If the system is lean at certain conditions, then the LONGFT PID would be a positive value at those conditions, indicating that increased fuel is needed.
The ability to identify the type of lean condition causing the concern is crucial to a correct diagnosis.