P1121 Changed Valve Again

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Dave Jeffries, Sep 2, 2025.

  1. Dave Jeffries

    Dave Jeffries Junior Member

    Joined:
    Jan 25, 2015
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    Location:
    Vancouver, WA
    Vehicle:
    2005 Prius
    Model:
    II
    In 2023, I was getting P1121 & P1123 on my 2005 Prius. In August 2023, I bought a genuine Toyota
    16670-21010. Today I changed out the valve AGAIN with a genuine Toyota part. So much for buying a OEM part!
    For about a year, I have been getting a CEL and after awhile, it would reset itself. Sometimes I reset the code with my tool. Usually checking to see that something else was not happening.
    In the last month, the CEL was staying on. I would reset the codes and they would set the CEL on the next startup. P1123 would be the lead code.
    After I changed the valve and bled most of the air out of the system, I did a test drive and noticed the CEL was off. Hope this lasts longer.
     
    #1 Dave Jeffries, Sep 2, 2025
  2. saneesh8

    saneesh8 Member

    Joined:
    Jul 5, 2024
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    Location:
    Allen, TX
    Vehicle:
    2009 Prius
    Model:
    One
    OEM part failed quickly? Any chance you can open it up and see what caused it? Hopefully the new one will last longer.

    P1121 - Coolant Flow Control Valve Position Sensor Stuck
    P1123 - Coolant Flow Control Valve Position Sensor Circuit High- Any loose connection?
     
    #2 saneesh8, Sep 3, 2025
  3. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
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    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    where did you buy it from?
     
    #3 bisco, Sep 3, 2025
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