2009 Prius P1121

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by PriusGenxFixer, Feb 27, 2026 at 3:37 PM.

  1. PriusGenxFixer

    PriusGenxFixer New Member

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    I have a 2009 Prius that has P1121 come up periodically
    Bought it used. Ran well for 5 years.
    Triangle of death with P1121 (after 5 years)
    Check engine again after 2 years
    Secong Check engine again after 2 more years
    I used an Coolant Control Value the first two times from Amazon. Check engine would go away after about 30 min of running vehcile

    What are your thoughts on the amazon product not being of good quality and if i need to go to a OEM Toyota unit
     
    #1 PriusGenxFixer, Feb 27, 2026 at 3:37 PM
  2. saneesh8

    saneesh8 Member

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    Aftermarket, avoid.. So many fake items. Just get the OEM.

    How many miles on it? i have the same year.. almost 158k on it.
     
    #2 saneesh8, Feb 27, 2026 at 4:57 PM
  3. PriusGenxFixer

    PriusGenxFixer New Member

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    I have 160k too :)
    I ordered one from ourismantoyotaofrichmond website. Had good reviews
     
    #3 PriusGenxFixer, Feb 27, 2026 at 5:35 PM
    Brian1954 likes this.
  4. BiomedO1

    BiomedO1 Senior Member

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    Have you tried flushing out your cooling system? You may have junk mechanically jamming up that switch valve or it could just be the cheap counterfeit part. :mad:o_O:whistle:
     
    #4 BiomedO1, Feb 27, 2026 at 6:20 PM
  5. Tombukt2

    Tombukt2 Senior Member

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    Bust the cheap fake part open remove the driver gear . And center the port blocking diverter . Now the motor will move but it's moving nothing so it thinks it working . And coolant is flowing through all ports .
     
    #5 Tombukt2, Feb 27, 2026 at 8:40 PM
  6. PriusGenxFixer

    PriusGenxFixer New Member

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    Tombukt2: Your response is adavnced, I cant understand a thing you just said. I know you have explained this 1000s of times to otheres. Can you kindly explain or point me where this is document for laymen like me?
     
    #6 PriusGenxFixer, Feb 27, 2026 at 8:48 PM
  7. Tombukt2

    Tombukt2 Senior Member

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    Take cover off cheap part there's a spiral gear inside under cover that moves a paddle around in an arc closing off a port wen called for . I lift the spiral gear out of case . Center the paddle that blocks off a port en moved . Close unit up . Reinstall plug it up . Start car . You should have heat and full coolant flow throughout system . I don't know if I have pictures of this . It's pretty self evident with screws out case open .
     
    #7 Tombukt2, Feb 27, 2026 at 8:54 PM
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