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Consumer Assistance

2000 Ford Explorer XLT System Too Lean

My 2000 Ford Explorer failed the emission test. I need to know what I need to do to pass.

The smog test results said Trouble Code P0171 Bank 1 System Too Lean and Trouble Code P0174 Bank 2 System Too Lean.

What is my problem and how can I fix it?


Trouble Code P0171 and P0174 on your Ford Explorer indicates your Ford's engine is running lean in both Bank 1 and Bank 2. Bank 1 is the side of the engine where the number one (1) cylinder is located. The oxygen sensor on bank 1 has noticed the engine is running lean. Running "lean" means either inadequate fuel is getting to the combustion chambers, or too much "unmetered" air is being mixed in with the fuel. First you'll need to look into things which would cause unmetered air to enter the intake manifold, such as cracked or disconnected vacuum hoses. "Unmetered" means air which is getting to the combustion chambers without passing through the mass air flow sensor. Next you should inspect things which would cause inadequate fuel delivery such as emission sensors which may be reporting false values to the ECU (engine control computer). A good example of an emission component which could be defective and causing inadequate fuel delivery is the MAF (Mass Air Flow Sensor). A good example of a mechanical component would be a dirty fuel filter or weak fuel pump. There is always the possibility of the Bank 1 and Bank 2 Oxygen Sensors being defective and not sending out the correct fuel mixture voltage, however it is recommended to suspect a defective oxygen sensor after inspecting the vacuum lines and the MAF.

posted by SmogTips Support 10-28-2013 11:13 PM

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