Hope this help, generic code emissions related.
P0171 System too Lean (Bank 1) link explains better than I could :)
this people have great info.
http://www.engine-light-help.com/oxygen-sensor-codes.html
Trouble code P0171 means: Bank 1 Combustion Too Lean
Trouble code P0171 means:System too lean (Bank 1)
Trouble code P0171 means:System too lean (bank 1)
Trouble code P0171 means:System too lean (Bank 1)
Trouble code P0171 means: System Too Lean (Bank 1)
trouble code P0420 means: Catalyst Efficiency Low - A Bank
Start with looking for a vacuum leak.
It is rich or lean bank 1 or 2 i am not sure which one it is but i know it is rich or lean code they have the same codes as ford.
P0171 = System too Lean (Bank 1). I would start by looking for a vacuum leak under the hood.
Trouble code P0171 means: Fuel System Too Lean (Cylinder Bank 1)
po171--- system to lean (bank # 1)
Trouble code P0171 means:System too lean (Bank 1)