In the manual for the 2000 Sentra, page EC-306, for DTC P0171, P0174 Fuel Injection System Function, it shows as possible causes:
- Intake air leak
- Heated oxygen sensor 1 (front) (bank 1) (bank 2)
- Injectors
- Exhaust fuel pressure
- Lack of fuel
- Mass air flow.
I have read that the Mass air flow sensors are prone to fail on these cars, so you might want to have that checked first.
Trouble code P0171 means System too lean (bank 1)
Trouble code P0171 means: Fuel Trim 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 P0171 means:System too lean (Bank 1)
Trouble code P0171 means:System too lean (Bank 1)
Trouble code P0171 means: Fuel System Too Lean (Cylinder Bank 1)
Trouble code P0171 means: System Too Lean (Bank 1)
Trouble code P0171 means:System too lean (Bank 1)
Trouble code P0171 means: Bank 1 Combustion Too Lean
Trouble code P0171 means: System Too Lean (Bank 1)