Quick fix for code p0446 evap emissions vent circuit low.

Discussion in 'How-to Guides' started by kinglt1, Feb 17, 2009.

  1. Macarchie

    Macarchie New Member

    Hello people... new to this thread.

    I have a 2006 GMC Sierra crew cab; 5.3L, Z71. About a year ago, it threw the P0446 code. I replaced the canister at that time. Since then, the CEL comes on about every 3 months with the same code. I would just clear the code and not worry about it. Now, it is time to get the bi-annual emissions test. I stopped by the GMC dealership and picked up another solenoid kit ($180 - ouch) and plan to put it on in the next few days. I assume the replacement solenoid I installed is bad but (being an electrical component) they won't take it back. I plan to blow out the line and replace the unit and canister. Is there anything else that I should do while under there?
    Question: What does this silly solenoid do? Does it serve any useful purpose or is it just un-necessary complication? Seems to me that a simple check-valve to allow a little air in when needed as fuel is being drawn out would suffice. <Gripe off>

    I have been a member of several other forums and appreciate the opportunity to learn from you guys. This thread has been particularly helpful :great:

    - Jimmy
  2. Bill1010630

    Bill1010630 New Member

    The first thing that needs to be checked with P0446 is if the fuel tank pressure sensor is reading correctly, with the fuel cap off it should read atmospheric pressure. If it reads correctly the vent solenoid is the likely culprit.
  3. j cat

    j cat Epic Member 5+ Years 1000 Posts

    this code can be from operating in dusty off road conditions or overfilling the fuel tank then parking after a short ride in a hot/warm area. avoid parking with the front end down when full..

    the vent lines get fouled with charcoal from the canister , when the overfill cause is responsible.
  4. Macarchie

    Macarchie New Member


    Thanks for the replies. Here is an update to my original post. I got under the truck to replace the unit and realized that the hose had a crimp in it. I cut a longer piece and used a wire tie to hold the longer hose away from the driveshaft. I reset the code and have driven it for the last week. I put the code reader on it and there are no pending codes. The problem is fixed. :great:

    - Jimmy
  5. EllenH

    EllenH New Member

    Hello, new to the site. I have the PO446 code on my 2000 Silverado 4x4 extended cab long bed. Tried to locate the canister but not sure I found the correct part. It was in between the cab and bed on top of the gas tank. Really hard to get to and wasn't able to disconnect it to try and blow it out. Can anyone post pictures of location and how to get it loose and disconnect the hoses for this year of truck? Thanks
  6. randomlyrob

    randomlyrob New Member

    I'm working on this issue in my 04 3500 6.0L. I have a P0446 & P0452 codes. Both the vent solenoid and fuel tank pressure sensor are new. The vent solenoid is the updated style with filter and the pressure sensor came with the new sending unit that I installed. The old unit was rusted out and leaking fuel everywhere. Thanks!
  7. MyDenaliSux

    MyDenaliSux New Member

    If one of the plastic lines were pinched, can you engineer a patch with regular vacuum line? I'm not sure if this is the reason for the p0446 code coming up once in a while, but I've checked everything and clean out as much as I can. The code started popping up when I replaced the fuel pump a few weeks ago. All the connections are solid. Also... everyone has pics of round canisters. The one on my Denali is like a rectangle-box. It's mounted forward on the side of the fuel tank. pic2.jpg pic3.jpg pic4.jpg
  8. j cat

    j cat Epic Member 5+ Years 1000 Posts

    go to the dealership and get a new line. this is not that expensive. 30 uSD..

    easy on these lines with these SUV types the lines must be carefully positioned on a tank drop/install..

    - - - Updated - - -

    with the pickup the canister is not on top of the fuel tank. the canister is between the fuel tank and frame rail. you will see hoses of 3 different sizes going to it . using tools to release the lock ring these slide off. if the hoses are with black crap inside you will need to clean replace these lines and the canister. do not over fill gas tank then park the vehicle..or fill up the fuel tank and put in a heated garage.
  9. P0446

    I just bought a 2002 Chevy Tahoe... And the service engine light has been on since I bought it. Scanned the truck and the code read P0446. Started doing reasearch online to try and narrow down my problem. Went to the parts house and the guy told me he would not sell me the Purge Vent Solenoid that I needed to go to the dealer.. (BUMMER) I called the dealership and made sure I had all the info I had found available for the conversation (being a female they tell you things that may not necessarly need to be done just to get more money). So they guy on the phone says they need to run a test $76.99+tax and then to fix the problem I am looking upward of $350.00.(I am by no means rich) So I decided today I was going to go to a different parts store and tell them I wanted the part, But now reading this I think tonight I am going to take the original part off the truck and try to blow it out and hope it fixes the problem...
  10. Macarchie

    Macarchie New Member

    It can't hurt. I hope it works for you. The plastic clip that holds it on may break when you try to get it off… You may need to get some hose clamps to secure it when you put it back on. Make sure the clamps are tight. The sensor is checking for a slight pressure and the check engine light will come on if the pressure differential is not correct. Before you remove it, you might want to check it good to ensure the hose is not cut or has a hole. If it is just a hole, you may be able to just patch it with tape.
    good luck.

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