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Recurring P0446 code

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Draken, May 1, 2014.

  1. Draken

    Draken Junior Member

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    Hello all, been having an issue with my 2005 Prius (186k miles) throwing the P0446 error code (Evap Emission Control System Vent Control Malfunction). It was in the shop twice last year for this. First time, diagnostic was clean, they replaced the gas cap, reset the light and sent me on my way. Happened again a day or two later. Back in shop, again diagnostic was clean. They contacted Toyota who had the tech manually cycle the valves. One was sticking every now and then, they replaced it. Now, just about a year later, code comes up again. Back in shop, they detect a minor leak, say gas cap wasn't seated. Cleaned it up, reset the light and off I go again. Week later, code is back. Tired of throwing money at the dealer so they can play eenie meenin minie mo trying to fix this. So I got a bluetooth ODBII scanner and run Torque Pro on my Android phone. I've attached the logs (CSV) from a trip home, about half way on that trip, the MIL came on again for the same code. Can anyone look at the sensor output and give me a better idea of what is going on? The Evaporative System Vapor Pressure seems to swing wildly, at least to me. Any help you all could provide would be greatly appreciated, and my wallet thanks you too!

    Cheers,
    James
     

    Attached Files:

    #1 Draken, May 1, 2014
  2. Draken

    Draken Junior Member

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    I should also mention that I click the gas cap two clicks when putting it back on after refueling.
     
    #2 Draken, May 2, 2014
  3. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Location:
    Green Valley, AZ
    Vehicle:
    2015 Prius
    Model:
    Two
    This is the full list of suspect items with DTC P0446. Consult techinfo.toyota.com for repair manual info if you wish to dive deeper:

    Fuel tank cap is incorrectly installed
    Fuel tank cap is cracked or damaged
    Vacuum hose is cracked, blocked, damaged or disconnected
    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
     
    #3 Patrick Wong, May 2, 2014
  4. Draken

    Draken Junior Member

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    I'm hoping someone with more knowledge on this subject can look at the ODBII logs and help narrow it down a bit, as that is a lot of stuff to check/replace trying to fix this issue.
     
    #4 Draken, May 2, 2014
  5. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Location:
    Green Valley, AZ
    Vehicle:
    2015 Prius
    Model:
    Two
    The reason that I provided the long list is to show you that many issues could cause the problem. After all, if it was so simple to fix the dealer tech would have already done that by now.

    If you are truly serious about doing something about the problem, you need to do the following:

    1. Buy Mini VCI, which runs on a Windows XP or Windows 7 32 bit OS laptop
    2. Subscribe to techinfo.toyota.com
    3. Follow the detailed troubleshooting steps (there are ten activities) associated with P0446, which requires you to remove and inspect several components associated with the fuel tank.
    4. When you see the troubleshooting tree involved, you will understand that for a complete job, the dealer service department could easily charge you for 4 hours of labor not to mention the parts markup. Is it worth it to you to save $500+ by DIY?
    5. Or of course, you could live with the car as-is.
     
    #5 Patrick Wong, May 2, 2014
  6. Draken

    Draken Junior Member

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    Sounds a bit too involved for my level of car knowledge. Is there any long term harm with ignoring the MIL and resetting it myself before taking the vehicle to the dealer for any service I have them perform? I need to get about 2 more years out of the vehicle but currently don't have funds for long, drawn out and potentially expensive troubleshooting and repairs for the P0446 code. But I'll do what I have to if it means the health and safety of the vehicle.

    Thank you
     
    #6 Draken, May 5, 2014
  7. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Vehicle:
    2015 Prius
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    There is no impact on vehicle health or safety. The impact is on the environment, as the fuel tank potentially is allowing gasoline vapor into the atmosphere.
     
    #7 Patrick Wong, May 5, 2014
  8. Draken

    Draken Junior Member

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    Thank you, appreciate the information!
     
    #8 Draken, May 6, 2014
  9. CatsAreGods

    CatsAreGods Junior Member

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    Mar 23, 2014
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    Location:
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    Vehicle:
    2006 Prius
    Model:
    ----USA----
    But if Draken keeps the car indoors and gasoline fumes build up, it could be dangerous in that case.

    Nexus 4 ?
     
    #9 CatsAreGods, May 6, 2014
  10. Draken

    Draken Junior Member

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    Shouldn't be any more dangerous than a 70's or 80's era vehicle kept in a garage. Or a lawn mower and other gas powered lawn equipment.
     
    #10 Draken, May 7, 2014
  11. 299K

    299K Junior Member

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    Location:
    Cleveland, OH
    Vehicle:
    2005 Prius
    Model:
    Base
    Hello all.
    Just started having this code on my 2005. Estimated 500k on her. When this code triggers the check engine light, it causes the ICE to run almost all the time. Did anyone ever figure out the solution to p0446? For now I just erase the code when the check engine light comes on, no other issues. I do have the spoofer installed, put it in during this past winter, no check engine light till the weather started getting warmer here.
     
    #11 299K, May 21, 2020
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