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Code P0446 Evap.....help....

This is a discussion on Code P0446 Evap.....help.... within the Technical / Maintenance forums, part of the General Discussion category; I would like to know if anyone has any pics as to where the fix needs to be performed is ...

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    Beware The Evil CrankToe LOHRTBT's Avatar
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    Code P0446 Evap.....help....


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    I would like to know if anyone has any pics as to where the fix needs to be performed is at? I just dont know where to start or what to clean out? lol
    Thanks!

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    Re: Code P0446 Evap.....help....

    P0446
    Evaporative Emission Control System Vent Control Circuit Malfunction


    EVAP stuff it hard to help with on the internet. Basically something is wrong with the vents on your fuelsystem/gas tank.

    Sorry man, I wish I could be of more help.

    here is alink that MAY help I found it by entering PO446 GM truck into a SEARCH engine.


    http://www.gm-trucks.com/forums/inde...59403&hl=p0446

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    Re: Code P0446 Evap.....help....

    Thanks man....I just need pix of the actual locations lol...I imagine that all the people have done it already could chime in and post a pic or 2 for those of us that are not sure where it is. :)

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    Re: Code P0446 Evap.....help....

    Ttt

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    Interstate A**-Hauler gman4dx266's Avatar
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    Re: Code P0446 Evap.....help....

    Make sure your gas cap is on. I have chased this around myself. :-P

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    Re: Code P0446 Evap.....help....

    I had a similar code on my Tahoe. The vent valve was flakey. Its a black box near the fuel tank about the size of a cigarette pack. It has a 2 wire harness (purple and yellow I think) and a 1/2 inch or so rubber line going to it. It houses a valve and an air filter and water, mud and crap gets in there and jams the valve piston. Remove the whole thing and then separate the filter housing from the valve housing by releasing some tabs and rotating the pieces.

    Give it all a bath and use compressed air to really dry out the valve and coil. You may need to use Q-Tips inside the piston bore. Check the valve by applying 12v to the terminals. I don't remember the polarity so only bump the power each way until it moves.

    My valve became weak so it only worked in the orientation it's supposed to be mounted.. coil up - piston down. When you find the right polarity, bump the valve with 12v many times in succession about 1 second apart. If it works 100% then you are done. Mine worked about 4 out of 10 times so I kept cleaning until it worked. I got it clean enough to reuse until I get around to ordering another (about $40).

    There is another related valve on the motor but I stopped troubleshooting when the one I just described was the culprit.

    It probably should be cleaned anyway so take the 30 minutes to do it and everything may be groovy. The computer checks it often (by testing if the fuel system will hold and release a vacuum - hence the reason a loose gas cap as noted above will also throw that code) so the CEL should clear in a few days if its working. It has to do with keeping fuel vapor out of the atmosphere and other EPA stuff so there shouldn't be any performance or damage issues involved.

    The other valve I mentioned that's on the engine provides the vacuum so it could be bad also.

    Greb
    Last edited by Grebbler; 11-06-2008 at 07:42 PM.

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    Re: Code P0446 Evap.....help....

    Quote Originally Posted by gman4dx266
    Make sure your gas cap is on. I have chased this around myself. :-P
    This is one of the most common problems I've seen. Make sure you tighten your gas cap until it clicks a few times. The first question I always ask is "when was the last time you got gas". I did have this code come up a couple weeks ago on my truck, but luckiliy it just turned out to be some wet snow clogging up the vent valve. Let it thaw, cleared the code, and it's been fine since.

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    Re: Code P0446 Evap.....help....

    I take it you see some dusty conditions from time to time. The vent valve is either on the back of the fuel tank or at the front of the fuel tank along with the canister. Seems like half tons the valve and canister mount at the front of the tank where they get filled with dirt. The diagnosis is disconnect the hose between the valve and canister and if there is dust present **** can it all and get a new valve and canister. GM did revise this somewhat if you could even call it that. The valves now are outfitted for an auxilary mounted filter box which is still a piece of crap but if you run it all the way up to under the hood and in the back corner of the engine bay behind the fuse block that is usually the only clean spot on a truck if there is one. Its really pretty easy once you've done one or 15 or 20.
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    Re: Code P0446 Evap.....help....

    Ok, So I finally got around to doing this today since I am off.

    Took me a few to find the stupid thing lol..but the easiest way I found to spot it is to look between teh bed and cab in the gap..and there it is.

    Anyhow, took out the old one and MY GOD it had some shizz in it!!
    This is about 3/4 of the dirt and rocks that came out of it. NO wonder it was not working haha.


    Called O'Reilly's ..they dont stock the new one, called GM, it was $27 bucks for the new design. The new one uses a new bracket, it was not purchased due to the fact that it costs !!!! $67 !!!! For a piece of metal with a hole in it lol.

    So I just zip tied it in place and dont forsee any issue with it in the future.

    Went down and reset the error codes and we will see if this fixes my issue with the SES light.

    OH yeah...the old part # is not good now, here is the new part # for those interested: ACD#214-2149
    GM # 25932571
    This is for the solenoid valve.

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    Re: Code P0446 Evap.....help....

    How hard was it for you to get this out? It seems to be a tight squeeze with the hose and harness connected. Did you just squeeze your hand in there and unplug the hose and harness? or did you remove anything to make it easier? I'm going to do this to my truck because I believe this is my problem.

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    Re: Code P0446 Evap.....help....

    Mine has the same code, have been debating on taking that thing off since it seems like a pain to get to.

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    Re: Code P0446 Evap.....help....

    I have had the same code on my 2001 GMC Sierra Ext. Cab 5.3L for a while now and I can't get my truck inspected because of the Check Engine Light. I replaced the vent valve and mounted it above the transmission just as the GM service bulletin says to do yet I still have the code after a reset. Anyone have any ideas? The code is P0446 Evap. System Fault

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    Re: Code P0446 Evap.....help....

    Read my post. You need a canister. If it gets dirt in the valve then its got dirt in the canister. Dirt = no flow.
    1995 Silverado - ported vortec heads, 4L80E, efans, LT4 Hot Cam, Rear disc brake conversion w/drilled and slotted rotors
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    Re: Code P0446 Evap.....help....

    is this the same part needed to be fixed on a p0449 code ?

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    Re: Code P0446 Evap.....help....

    Quote Originally Posted by Southern bred
    is this the same part needed to be fixed on a p0449 code ?
    That may be a vent valve issue as well. That code basically says the voltage supply to the vent valve, or the voltage drop across the vent valve isn't what the PCM is wanting to see which should be right around ignition voltage.
    1995 Silverado - ported vortec heads, 4L80E, efans, LT4 Hot Cam, Rear disc brake conversion w/drilled and slotted rotors
    1999 NBS Silverdo - transgo HD2 shift kit, 3 inch dynomax ultra flow, Ford keys and 305/70-16 Mickey ATZs

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    Re: Code P0446 Evap.....help....

    So yeah looks like you were right, the light came back on so I will be replacing the canister next.

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    Re: Code P0446 Evap.....help....

    anyone know how to get the vaccum line off ?

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    Re: Code P0446 Evap.....help....

    anyone know how to get the vaccum line off ?

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    Re: Code P0446 Evap.....help....

    I have the same issue on my 04 Avalanche. To answere the above question, I used a screw driver to pry the black plastic tabs back while pulling on the line. It will come off, just keep pressure on it and gently pry on the plastic tabs.

    Also, I am curious if anyone has found a fix for this other than the vent selenoid? I have changed the Selenoid and hose going to the vent box. The check engine light comes on shortly after every refuel. I have replaced the cap and clicked it until i'm blue in the face....Is there another part I should look into? I have heard people on here say that fuel was getting in the vent box. What part will allow this to happen?

 

 

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