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O2 Sensor Locations

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by priusde, Aug 6, 2016.

  1. priusde

    priusde Junior Member

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    Trying to replace the post cat O2 but not sure if I have the right location. Anyone have a diagram?
     
    #1 priusde, Aug 6, 2016
  2. NutzAboutBolts

    NutzAboutBolts Senior Member

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    It should be after the cat and there should be only 1 after the cat.
     
    #2 NutzAboutBolts, Aug 6, 2016
  3. priusde

    priusde Junior Member

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    Is this it (photo)? It's the only one I see and it appears to be before the cat.
     

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    #3 priusde, Aug 6, 2016
  4. Raytheeagle

    Raytheeagle Senior Member

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    That appears to be the one before the cat. Look further back along the exhaust and it will look similar. Any reason for replacing the oxygen sensor after the cat? Rarely any issues with that sensor. Usually the one in front of the cat has more problems.
     
    #4 Raytheeagle, Aug 6, 2016
  5. priusde

    priusde Junior Member

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    About how far back after the cat should it be because am not seeing it.

    Old engine had big head gasket leak, probably ended up fouling the cat. It's throwing the PO420 code and I wanted to put on a spacer to pass emissions before spending big money on a factory cat.
     
    #5 priusde, Aug 6, 2016
  6. Raytheeagle

    Raytheeagle Senior Member

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    Away from my house now, but will snap a shot when I get back. How many miles on her before the head gasket went? Any idea what the cause was?
     
    #6 Raytheeagle, Aug 6, 2016
  7. Raytheeagle

    Raytheeagle Senior Member

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    .
     
    #7 Raytheeagle, Aug 6, 2016
    Last edited: Aug 6, 2016
  8. priusde

    priusde Junior Member

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    Not sure exactly what it was as I bought the car this way from previous owner at 230k. I just ended up replacing the engine.
     
    #8 priusde, Aug 6, 2016
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  9. Raytheeagle

    Raytheeagle Senior Member

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    Reliving at
    After looking under the hood, the upstream oxygen sensor can be reached by removing the wipers from above or probably from underneath by removing the splash guard.

    The picture you took earlier looks like it was from underneath looking toward the front of the car.

    That should be the downstream oxygen sensor as the cat is in front of it and the resonator is downstream of it. Hope it solves the code for you. On eBay or a salvage yard you probably could get a cheaper cat and exhaust setup. Sounds like you are familiar with that though:).
     
    #9 Raytheeagle, Aug 6, 2016
  10. priusde

    priusde Junior Member

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    Aha so that is the post cat, lol. Too dark now but will get at it tomorrow, thanks for the help.
     
    #10 priusde, Aug 6, 2016
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