Possible Causes
WARNING: This page is about a different car, the 2003 Nissan Pathfinder. However, it is still accessible from the selected car via links, so may be relevant.
ECM illuminates MIL and sets DTC P0171 when Bank 1 fuel mixture ratio compensation amount is too large (mixture is too lean). ECM illuminates MIL and sets DTC P0174 when Bank 2 mixture ratio compensation amount is too large (mixture is too lean). Possible causes are:
- Intake air leaks.
- Poor, loose, corroded or damaged terminal connections.
- Defective HO2S 1.
- Defective injectors.
- Exhaust leaks.
- Fuel pressure incorrect.
- Lack of fuel.
- Defective MAF sensor.
- Faulty PCV hose connection.