Code P0171 Lean 2000 Ford Explorer – SOLVED

2000 Ford Explorer

I have a 2000 ford explorer with a v6 4.0 L. check engine light came on and it says its running lean on bank 1 and 2. What do I need to fix it and will it hurt the car to drive it?



The most common cause for this issue on this specific vehicle would be a vacuum leak. Specifically a cracked intake manifold. There is a TSB on this issue. Confirming the leak would be the first step. you can do this with the use of a smoke machine as recommended in the TSB. Or you may spray starting fluid along the intake with the engine running. As for driving it like this, go ahead. You will just have horrible fuel mileage until you get it fixed.

Ford Code P0171 – Fuel System Too Lean

Trouble Code Conditions:
Engine started, engine running at cruise speed for 3 to 4 minutes, and the PCM detected the Bank 1 Adaptive Fuel Control System reached its rich correction limit (a lean A/F condition).

Code P0171 Possible Causes:

  •  Air leaks after the MAF sensor, or leaks in the PCV system
  •  Exhaust leaks before or near where the HO2S is mounted
  •  Fuel injector(s) restricted or not supplying enough fuel
  • *Fuel pump not supplying enough fuel during high fuel demand conditions
  •  Leaking EGR gasket, or leaking EGR valve diaphragm
  •  MAF sensor dirty (causes PCM to underestimate airflow)
  •  Vehicle running out of fuel or engine oil dip stick not seated

Carefully inspect the following areas for potential air leaks:

  • Hoses connecting to MAF sensor assembly.
  • Hoses connecting to throttle body.
  • Intake manifold gasket leaks.
  • PCV disconnected.
  • Vacuum lines disconnected.
  • Improperly seated engine oil dipstick, tube, and oil fill cap.
  • Exhaust leaks at flanges and gaskets.
Ford TSB #01-20-5

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