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P0456 code options

Discussion in 'Technical Chat' started by whistler, Apr 26, 2012.

  1. Apr 26, 2012 at 4:36 AM
    #1
    whistler

    whistler [OP] Member

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    Greetings!

    Been reading several threads on OBD2 codes and fixes here on the board, and it's been quite an education. Just have one question . . .

    My CEL came on yesterday morning on the way to work, so I stopped by Autozone on the way home and had them read the code in question. Per the code, it's an EVAP issue.

    I changed gas caps, but that didn't change anything. I'm prepared to replace the canister, but what other components might be suspect? I'll replace whatever's necessary, but I'm not sure how far into the weeds I'll need to go. I've had only one CEL come on in my driving life (I'm 52), and that was at 123K miles on an old Datsun, not the measly 42k miles on my Tacoma.

    Thanks for any info you can spare.
     
  2. Apr 26, 2012 at 9:22 AM
    #2
    Ga tacoguy

    Ga tacoguy Well-Known Member

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    Rudy
    Augusta Ga.
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    :) Let's see if there is a way to fix this problem. My brother's PT cruiser is having this same problem, and we have been trying to find it for a while, so I know this is not a easy fix. My book says that we are looking for a tiny leak in the evap system. It describes a Large leak as a hole that is .040 of a inch, which is the size of a hole that a thumb tact makes,so this is a tiny leak to find.
    The first thing to do is to check all the vacuum hoses you have to see if they are bad or collapsing. Sounds easy doesn't it :rolleyes:, since you have done the most popular fix, replace the gas cap and usually the wrong one. There are hoses under the hood and connected to the gas tank and it is a pain to start looking for all the possibilities. I would look at your hoses, disconnect them one at a time, if possible and plug one end of the and blow air into the line either with a mityvac pump or blow into the line with your mouth, which is nasty, but quick way to check. When you encounter a connection,like the clamp that hold the gas filler tube to the gas tank, I believe it is a simple screw clamp that can be tightened, this kind of thing could be part of the leak.
    There is no easy answer to this problem, it is so tiny,but it will make the light come on. I would look at your vacuum lines and check them if you can and tighten all the connections that go to the gas tank and to the gas lines and see if any are loose. You may never find the solution,but you may fix it and not know you did. Just look at the lines and fix any if needed and wait for the light to come back on again. If it comes on with the same code, then more stuff may be needed.
    There is a way to check this with a smoke generator and has to be done by a mechanic, but this is expensive and I hope the last hope to find the problem. Good Luck.
     
  3. Apr 26, 2012 at 9:28 AM
    #3
    98tacoma27

    98tacoma27 is gooder 'en chicken Moderator

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  4. Apr 26, 2012 at 12:01 PM
    #4
    Ga tacoguy

    Ga tacoguy Well-Known Member

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    :) Thanks Ben, that is a useful piece of information you posted there. It helps define what you need to look for at the top of the page.
    1. fuel tank cap--Done
    2. Leak from Evap line from the Evap canister to the fuel tank. There is a vacuum diagram located under the hood of your taco. It should show where the major connectors are and where they go to. Following the evap line under the truck to the tank is a pain, but since this is a small leak, I would go straight to the tank and look at the line going in and see if it loose or looks cracked.
    3.Leak from Purge valve to Evap canister, You will need to look at the diagram to see where it is and what it shows. Most canisters are mounted on a fender or nearby.
    4. Leak from gas tank, I would look at the connections from the fill hose to the tank first, than look at the lines. I hope there is no leak from the tank.
    5. A leak from the canister, this could happen if you have overfilled your tank to the brim of the filler neck or done a lot of aggressive off road driving. You may be able to look at the canister to see if it looks like gas has come out of it or smells like gas. You may be able to shake it and get some gas out or let it dry out if possible, at worse you would need to get another evap canister.
    This should give you a good idea of what to look for. Good Luck.
     
  5. Apr 27, 2012 at 3:14 AM
    #5
    whistler

    whistler [OP] Member

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    Gentlemen, thank you very much for the info! I really appreciate your help!

    Ed
     
  6. May 11, 2012 at 7:30 AM
    #6
    jeratbp

    jeratbp Well-Known Member

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    Went to Advance Auto and used the scanner to pull this code. Looks like I will start with replacing the Gas cap.

    Thanks for the info.
     
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