Every 4 or 5 days I get a P0456: evap emissions system, small leak detected

Discussion in 'Gen 2 Prius Main Forum' started by MilkyWay, Nov 11, 2017.

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  1. MilkyWay

    MilkyWay Active Member

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    Seems like a hard issue to track down root cause. Would it be wasteful to replace gas cap?

    The light never comes on while I am driving. What usually happens is if I let it sit for 12-15 hours I'll start the car and it will remain on.

    I then delete it and it stays off for about a week.
     
    #1 MilkyWay, Nov 11, 2017
  2. ChapmanF

    ChapmanF Senior Member

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    It is coming back about as often as the car does its automated test for small leaks, which it does during hours while it is turned off. So you have a small leak. The repair manual has techniques for finding the leak and fixing it. There's also a more comprehensive training guide on it.

    It can be helpful to have a regulated, very low pressure supply of nitrogen (never use air, never exceed the (very small) pressure on the warning label of the evap test port). So if that sounds too fiddly, you might want to have a shop track it down.

    -Chap
     
    #2 ChapmanF, Nov 11, 2017
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  3. MilkyWay

    MilkyWay Active Member

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    Well, 1 year later I finally decided to fix problem!

    I am pretty sure it is fixed, but it has only been about 10 days.

    Shop did evap test and said it was the fuel filler neck.

    $150 for them to install (was also $60 for them to do diag).....And part was around $150. So $360 later I believe problem is gone.

    It really seemed to hate the cold as the light would come on much faster after sitting in cold weather...And it is cold and hasn't come back. So probably fixed. Also has 192k miles on it now.

    20181027_112223.jpg
     
    #3 MilkyWay, Nov 20, 2018
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