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Fault code p0171

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by moha777, Jun 5, 2020.

  1. moha777

    moha777 Junior Member

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    Hi
    As I have replaced both 02 sensors in my 2008 Prius with 189k miles its throwing another code with engine power loose.with red triangles lights on once fault code resetted I am getting engine management light in few miles drive.i have attached the fault code anyone experienced the same please advise. 20200605_121720.jpeg

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    #1 moha777, Jun 5, 2020
  2. JC91006

    JC91006 Senior Member

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    Did you use Denso parts? Many aftermarket o2 sensors don't work well with the car.
     
    #2 JC91006, Jun 5, 2020
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  3. ChapmanF

    ChapmanF Senior Member

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    So the sensors are saying the mixture is lean.

    That doesn't always mean the sensors are bad. Sometimes the mixture is lean. It's their job to sense that.

    Can that reader show the bank 1 long term fuel trim?

    Have you checked for intake leaks, low fuel pump pressure, injector issues?
     
    #3 ChapmanF, Jun 5, 2020
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  4. moha777

    moha777 Junior Member

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    But my auto electrician told me that's the fault.but I need to get fuel pressure and injectors checked

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    #4 moha777, Jun 7, 2020
  5. dolj

    dolj Senior Member

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    What exactly did the auto electrician say?


    P0171 doesn't necessarily mean the O₂ sensor is broken.

    DTC P0171 System Too Lean (Fuel Trim)

    Trouble Areas:
    • Air induction system
    • Injector has blockage
    • Mass Airflow meter
    • Engine coolant temperature sensor
    • Fuel pressure
    • Gas leakage in the exhaust system
    • Open or short in A/F sensor (bank 1 sensor 1) circuit
    • A/F sensor (bank 1 sensor 1)
    • A/F sensor heater (bank 1 sensor 1)
    • EFI M relay (integration relay)
    • PCV valve and hose - PCV hose connection
    • ECM
     
    #5 dolj, Jun 8, 2020
    Last edited: Jun 8, 2020
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