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02 with code 171

Discussion in 'Generation 1 Prius Discussion' started by bigblock67, Nov 13, 2020.

  1. bigblock67

    bigblock67 433K with new cells

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    Rough idle and neither fans are coming oom leading to overheating
    Also codes 300 ; cylinder misfire
    What would be the obvious setting a 171 code?
     
    #1 bigblock67, Nov 13, 2020
  2. Josey

    Josey Active Member

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    P0171 is a lean condition reported by the upstream O2 sensor. A lot of people say to replace the sensor, but that can end up being shooting of the messenger. It is plausible that a true lean condition could lead to multiple cylinder/random misfires (P0300).

    But your real priority is the fans and the overheating. I'd not worry about the rest until that is straight. You'll want to hope that overheating didn't warp the head / kill the head gasket which could also produce a P0300.

    You really haven't given much info to go on.
     
    #2 Josey, Nov 15, 2020
  3. bigblock67

    bigblock67 433K with new cells

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    the rough idle and the codes 171 and 300s came before it got hot only once. No change is running. Don’t believe head is damaged. Do the fans not operating relate to 171. Or separate code for that
    Thanks
     
    #3 bigblock67, Nov 15, 2020
  4. Josey

    Josey Active Member

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    There are separate fan codes (P048x), and Toyota might have some special ones too. But it's got nothing to do with the lean report or the misfires.

    Do you have a scantool with which you can graph O2 sensor data and fuel trims?

    I would clean the MAF sensor and check for vacuum leaks, including around the intake manifold gasket and throttle body.
     
    #4 Josey, Nov 15, 2020
  5. bigblock67

    bigblock67 433K with new cells

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    Ok will do that check. Need a better ob2 scanner. Need more detail
    Thank you
     
    #5 bigblock67, Nov 15, 2020
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