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Annoying PO456 code....

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Jim Caldwell, May 10, 2015.

  1. Jim Caldwell

    Jim Caldwell Member

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    Its a 2009 Prius with about 75K miles on it. I have scangauge on the dash as well as mini-VCI. It is setting PO456 code time after time. I reset it, but it comes back in about 50 mils of driving. Its not the gas cap, I turn it until it clicks every time. Something is wrong with evaporative emissions system, which I wouldn't care about, except it might mask some other fault code that is more serious, as it keeps check eng. light on all the time.
     
    #1 Jim Caldwell, May 10, 2015
  2. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    How many gas caps have you tried?
     
    #2 JimboPalmer, May 10, 2015
  3. bisco

    bisco cookie crumbler

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    maybe it's the scan gauge. are you getting any lights?
     
    #3 bisco, May 10, 2015
  4. valde3

    valde3 Senior Member

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    Maybe OP should first check it with another fuel cap.
     
    #4 valde3, May 10, 2015
  5. exstudent

    exstudent Senior Member

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    Try:
    1) replacing the seal in the threaded edge of the gas cap; that is a wear item.
    2) a new gas cap, or a gas cap for a friend's Prius that isn't throwing codes.
    3) have you topped off? Maybe the fuel filler neck or other vales related to the tank/bladder are clogged or stuck in the wrong position, requiring replacement.

    EDIT:
    Bentley states, P0456 is same as DTC P0442
    P0442 - Evaporative Emission control System Leak Detected (small leak).
    Trouble areas to resolve:
    • fuel tank cap correctly installed
    • fuel tank cap is cracked or damaged
    • vaccum hose cracks are blocked, damaged, or disconnected in Figure 1 of the circuit description; reference the circuit diagram for the fuel system
    • open or short in vapor pressure sensor circuit
    • vapor pressure sensor
    • open or short in VSV circuit for EVAP
    • VSV for EVAP
    • open or short in VSV circuit for CCV
    • VSV for CCV
    • open or short in VSV circuit for pressure switching valve
    • VSV for pressure switching valve
    • fuel tank is cracked or damaged
    • charcoal canister is cracked or damaged
    • fuel tank over fill check valve is cracked or damaged
    • ECM
    Let us know what the solution was.
     
    #5 exstudent, May 10, 2015
    Last edited: May 10, 2015
    Dino33ca likes this.
  6. new.to.prius

    new.to.prius Junior Member

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    Extend warranty
     
    #6 new.to.prius, May 11, 2015
  7. 69shovlhed

    69shovlhed Surly tree hugger

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    +1 try a different gas cap 1st. can't assume the cap is good. or emissions stations can check your cap with their tester (if your state has emissions testing).
     
    #7 69shovlhed, May 11, 2015
  8. exstudent

    exstudent Senior Member

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    Extended warranties are typically a waste of money for most consumers. These insurance companies are in the business of making money for themselves. Their underwriters know the odds/longevity/probability of the covered components failing. A few people here/there may win the lotto and have a big ticket item covered, but the vast majority of the time, these companies make MONEY! Besides, these warranty policies have a lot of exclusions/loop-holes.

    Found the fuel/EVAP system training guide; its intense. Hopefully a known working gas cap will solve the problem.
     

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    #8 exstudent, May 12, 2015
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