2008 - P0446 Evaporative Emission Control System Vent Control

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by FantasticalMagicOne, Jul 30, 2022.

  1. FantasticalMagicOne

    FantasticalMagicOne Active Member

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    Hello,

    My 2008 Prius 192k+ miles has been throwing P0446 Evaporative Emission Control System Vent Control. I replaced the gas cap a few weeks ago and the CEL is still on. I know a number of things can throw this code and I'm not well versed enough to interpret the freeze frame data nor do I know if it would help narrow it down. I've attached it here in .pdf form and highlighted the same blocks that techstream did when I ran the health check. I appreciate any guidance anyone is willing to offer. Thanks.
     

    Attached Files:

    #1 FantasticalMagicOne, Jul 30, 2022
  2. Rmay635703

    Rmay635703 Senior Member

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    Likely not the case but mine had both a leaky fuel line and a hole in the vent line from the tank to the canister .

    usually have to find the leak
     
    #2 Rmay635703, Jul 30, 2022
  3. Tombukt2

    Tombukt2 Senior Member

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    In my sienna which is a Toyota van there's a vent valve or vacuum switching valve back near my gas tank that goes bad and is a known issue in this vehicle our Prius may have the same I don't know where is it where it is but it would be a VSV possibly in the rear of the car for the evap system I'm not where I can look at a schematic right now.
     
    #3 Tombukt2, Jul 30, 2022
  4. mr_guy_mann

    mr_guy_mann Senior Member

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    Evap system faults can be tough to figure out- for anyone. Most of the parts are located on top of the fuel tank, and access is bad. Really all you can do is try to perform the bidirectional tests to check function of the purge solenoid valve (on the engine near the water pump belt), the bypass solenoid valve (located on the evap canister on top of the rear of the fuel tank) and the leak detection pump (located on top of the right front corner of the fuel tank). Trigger each test and try to listen for (or feel if you can put fingers on each part) the part clicking when commanded on.

    I don't remember if a Gen2 will let you monitor what each step does during the automated Evap system function test. If it does then that should give you data to see what part fails.

    Posted via the PriusChat mobile app.
     
    #4 mr_guy_mann, Jul 31, 2022
  5. SFO

    SFO Senior Member

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    #5 SFO, Jul 31, 2022
    FantasticalMagicOne likes this.
  6. FantasticalMagicOne

    FantasticalMagicOne Active Member

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    Thanks! I haven't actually left, I just haven't had an issue where I needed to log in!

    This is what popped up when I rant the EVAP purge VSV which did turn on and off but that Vapor Pressure Tank reading seems way off the charts - unless I'm understanding it wrong. I read that the temperature of the gas has a direct affect on the pressure reading and we have had very high temps outside since the CEL turned on.

    I'm also not sure what other tests I'm supposed to run. I have a currently have a full tank - am I supposed to have a lower fuel level to test some of these things?
    upload_2022-7-31_10-37-0.png
     
    #6 FantasticalMagicOne, Jul 31, 2022
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