Check Engine Scan Gauge Code P0456

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by priusFTW, Jan 5, 2009.

  1. priusFTW

    priusFTW Gen III JBL non Nav

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    Hi everyone,

    Started my Prius this morning and got a check engine light. Scan gauge pulled code P0456. I did a search and got nothing. Anyone have any idea what this code is?

    Thanks!
     
  2. Patrick Wong

    Patrick Wong DIY Enthusiast

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    DTC P0456 Evaporative Emission Control Leak Detected (Very Small Leak)

    First, verify that your fuel cap is installed and has produced at least one click when you turn it clockwise. Also look at the rubber O-ring gasket on the cap and make sure it is in good shape.

    If your fuel cap is good and installed tightly, then the problem could be a sensor, a vacuum valve, or damage to the charcoal canister or fuel tank.

    Pls tell us what your refueling practices are - when do you refuel, and after the pump clicks off, how much additional fuel do you continue to pump into the system.
     
  3. priusFTW

    priusFTW Gen III JBL non Nav

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    Thank you very much Patrick for your reply! When I get out from work, I will check the cap. The last time I filled up was on Friday. I do not EVER top off the tank. The last time I filled the pump station was kind of awkward to get in to, so I may not have installed the cap properly. I will check it.

    Thanks again for your help!
     
  4. Mike Dimmick

    Mike Dimmick Active Member

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    P0456 is a standard OBD-II code which indicates a small leak in the EVAP system, which stops fuel vapours escaping into the atmosphere. It can indicate a loose or badly-fitting gas cap.

    If you've just refuelled recently, ensure the gas cap is screwed home correctly. IIRC after a few READY cycles, any non-critical conditions that are no longer current are cleared (the MIL light goes off).

    The preliminary manuals collection at Index of /Documents_2004/ lists, in the 05 - Diagnostics.zip collection, document cip0442.pdf, lists the conditions for the check and the possible trouble area. As follows:

    Fuel tank cap is incorrectly installed
    Fuel tank cap is cracked or damaged
    Vacuum hose is cracked, blocked, damaged or disconnected (any of the hoses in the EVAP system)
    Open or short in vapor pressure sensor circuit
    Vapor pressure sensor
    Open or short in EVAP VSV circuit
    EVAP VSV
    Open or short in CCV circuit
    CCV
    Open or short in VSV for purge flow switching valve circuit
    VSV for purge flow 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

    CCV = charcoal canister closed valve
     
  5. Patrick Wong

    Patrick Wong DIY Enthusiast

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  6. priusFTW

    priusFTW Gen III JBL non Nav

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    Just as an update, I went out to my Prius at lunch. I examined the gas cap. I cleared a little bit of ice that was laying in the valley where the gas cap screws on. I cleaned the cap and inspected the o ring. I screwed the cap back on. I cleared the code on my scan gauge and the check engine light went off and hasn't come back on. I believe that was the issue. Thanks guys!
     
  7. bedrock8x

    bedrock8x Senior Member

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    The 2006 manual is also available.

    http://www.selidori.com/tech/prius/doc/

     
  8. Patrick Wong

    Patrick Wong DIY Enthusiast

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  9. avocadoman1

    avocadoman1 Member

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    2006-155K miles
    got the P0456 code (very small EVAP leak)
    I live in CA which now requires a SMOG test every two years, even on Prius (what a scam).
    so I had to get the code cleared and vehicle functioning properly to get car registered.

    First, I purchased a new gas cap, cleared the code, no luck. code returned in 7 days
    Second, I took vehicle to a qualified hybrid mechanic who performed smoke test, took several hours, did not find a leak but located an intermittent solenoid valve
    $110 to diagnose + $125 to replace = $235

    7 days later the P0456 code returned
    Third, so i returned vehicle to same mechanic who claimed to have spent 4 hours (at no charge to me) trying to find said leak
    finally discovered a tiny smoke leak between the gas tank and the body
    they are now dropping the tank for an additional $175 (includes re-installing the tank)
    we will see what they find and how much more it'll cost me.
    that is, did the solenoid actually create the code? did i need a new solenoid?
    i'll let you know what i find out

    [​IMG]
     
    #9 avocadoman1, Sep 25, 2015
    Last edited: Sep 25, 2015
  10. bisco

    bisco cookie crumbler

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    i thought salvage title were exempt from smog? all the best!(y)
     
  11. avocadoman1

    avocadoman1 Member

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    UPDATE:
    it's a very tiny pinhole in the gasket seal between the fuel pump and the fuel tank
    the word is that i cannot purchase the fuel pump gasket separately
    in fact, the word is that i cannot even purchase the pump w/ gasket separately from the tank
    go figure

    the only way to repair this tiny pinhole leak is to purchase the fuel tank assembly that includes pump with gasket
    cost is about $550 for new + the $175 tank drop & re-install
    i'm researching a used tank w/pump, or make-shift gasket material options

    that is...a tiny pinhole leak, the vehicle performs fine but with the check engine light i cannot get it registered
    meanwhile I currently have $235 + $175 invested with potentially $550 more = $960

    [​IMG]

    more to come...
     
    #11 avocadoman1, Sep 25, 2015
    Last edited: Sep 25, 2015
    C Wagner likes this.
  12. avocadoman1

    avocadoman1 Member

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    in CA, nothing much exempts you from SMOG. not even Salvaged title
    like i previously stated, 2015 is the first year that CA is requiring hybrids to be smogged
    and I'm told its a quick diagnostic test only.
    plug into the OBD2 connector, get a reading. that is, nothing place up the tailpipe.
    $50 for a 5 minute test
     
    #12 avocadoman1, Sep 25, 2015
    Last edited: Sep 25, 2015
  13. bisco

    bisco cookie crumbler

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    maybe you can check with vw for some 'help' with the test.:cool:
     
  14. avocadoman1

    avocadoman1 Member

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    great news!
    the gasket can be ordered from Toyota for $10
    will arrive in a few days and be installed
    so my total outlay will be $235 + 175 + 10
    then i can pay my $50 for the SMOG test
    will update the Forum if repair does not work properly
     
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  15. brjafa

    brjafa Junior Member

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    Hello,

    I have been getting this code for the last couple of weeks now. I have reset the code with my scanner, but it has come back several times after about a hundred miles of driving and resetting the code each time. I made sure to really close the fuel cap each time I fill up, so I do not think that it is a loose cap (on my part) that is the issue. I also wiped down the cap to get rid of any foreign material, and the o-ring looked pretty good.

    Do you think that this issue is something that I need to act on now, or can I let this slide until my inspection in about four months. I don't want this to hurt my car in the long run.

    Thanks!
     
  16. C Wagner

    C Wagner Member

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    I’d love to hear more about this. I have a similar situation. Mechanic is saying “probably needs new tank”. If a gasket would do it instead…
     
  17. mr_guy_mann

    mr_guy_mann Senior Member

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    You don't know what it would take to fix the problem without testing. That testing could involve removing the gas tank and checking it for leaks out in the open. Could just need a new gas cap (get one from Toyota), or it could need a gas tank assembly. Or a hose, line, canister, or valve outside the tank. Could be one (or more) of a few dozen possibilities.

    The code indicates that the ECM determined that the fuel EVAPorative emissions system has a very small leak (more than 0.020" but less than 0.040") SOMEWHERE . That includes the gas cap, filler pipe, tank, all the vapor lines and stuff all the way up to the purge vacuum solenoid valve on the engine.

    Posted via the PriusChat mobile app.
     
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  18. C Wagner

    C Wagner Member

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    Yes, I'd agree that replacing the gas cap is a good thing to do first. I did that first with a Toyota OEM expensive cap. You could always resell it as 'nearly new' on Ebay - or keep it. $50 is outrageous, yes, but small in the overall scheme of the battle to stop P0456. In my case, my mechanic and the local Toyota sound like they don't want to bother with the work. Both quote $3,000 for 'probably a new tank.' I found a video on youtube showing how to open the inspection hole below the rear bench seat to see if the gasket there looks cracked or smells. I might try a third mechanic. Anyone know any prius-only or heavy into prius shops in Metro-Boston, MA?
     
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