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EVAP code help

Discussion in '1st Gen. Tacomas (1995-2004)' started by chrskpln, Jul 19, 2022.

  1. Jul 19, 2022 at 8:20 AM
    #1
    chrskpln

    chrskpln [OP] Active Member

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    Here’s the problem:

    Code p0446 on Tacoma 2002 2.7L


    It started with a few other codes related to the EVAP, which led to my replacing of the:
    fuel sending unit gasket
    Charcoal Canister
    Fuel Filler Neck (OEM)
    Gas cap (OEM)
    VSV in the engine bay

    When I took it to the mechanic to see if they could do a smoke test, all they could tell me was that smoke was getting out near the vent hoses connected to the fuel filler neck before I swapped that out, which cleared the p0440, but not the p0446. They recommended I swap out one of the VSVs.

    any thoughts?
     
  2. Jul 20, 2022 at 4:14 PM
    #2
    chrskpln

    chrskpln [OP] Active Member

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    UPDATE: The p0440 came back on as well.
     
  3. Jul 20, 2022 at 9:18 PM
    #3
    Dm93

    Dm93 Test Don't Guess

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    You really need to use a scanner and see what the vapor pressure sensor is reading to make sure it's not skewed (with the gas cap off it should read atmospheric pressure or 3.0-3.6 volts), if it's not either the vapor pressure sensor is bad or there's a wiring problem between the sensor and ECM.
    Also have you checked/replaced the lines and hoses related to the EVAP system?
     
  4. Jul 20, 2022 at 10:00 PM
    #4
    chrskpln

    chrskpln [OP] Active Member

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    I have not checked the hoses myself, but the mechanic said they were ‘fine’. I might need to perform my own smoke test. What scanner should I use? Mine says N/A for EVAP stuff (PCT and VP)
     
  5. Jul 21, 2022 at 1:57 PM
    #5
    CrustyTaco

    CrustyTaco Well-Known Member

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    I was fighting the evap codes for a long time until I pulled the bed and replaced all of the rubber gaskets and lines attached to the gas tank. I replaced my gas tank and fuel pump while I was in there, but my tank was pretty rusty. If you aren't in the rust belt you can probably get away with just replacing the gaskets.



     
  6. Jul 21, 2022 at 2:11 PM
    #6
    tirediron

    tirediron Well-Known Member

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    The first thing that comes to mind that explains both codes is a vent valve which is stuck open, and or intermittently faulty. You don't mention the vent valve being OE, but even if it is, entirely possible it was faulty out of the box. Rather than firing the parts cannon, or going to a shop where the best they can do is say that smoke is coming from a general area is to go to a reputable shop and have them actually diagnose the problem.

    This probably isn't hard to do on your own, but you will likely need both a smoke machine (you can make one yourself for <$25 - LOTS of 'How to' guides on YouTube) and a scan tool with bidirectional controls and live data capability so that you can operate the vent valve and other emissions system components as well as monitor system pressure/vacuum, etc. You also need the knowledge and experience to interpret the data the system is giving you.
     
    Sweet Crude likes this.
  7. Jul 21, 2022 at 3:08 PM
    #7
    chrskpln

    chrskpln [OP] Active Member

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    @CrustyTaco, I forgot to mention that I replaced each of those as well. New fuel tank and gaskets for the fuel pump and other valves. The fuel pump gasket was nasty and leaking fuel from the top, which is what I thought the codes were originally attached to in the first place. The only thing in the pictures that you sent me that I have not replaced is the hose at the bottom. Thanks for the informative reply, I probably should have stated those things earlier.

    @tirediron, I bought the AISIN green VSV and plugged that in, which did not seem to help the problem. Also, fair point on the reputable shop; however, I'm trying my best to save money and would like to avoid that if possible. I'm working on getting my own smoke test together. What bidirectional scanner do you recommend?
     
  8. Jul 21, 2022 at 5:41 PM
    #8
    Black DOG Lila

    Black DOG Lila Well-Known Member

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    @chrskpln the green Aisin VSV is EGR valve located top middle of engine.
    EVAP VSV (Purge Selnoid) is EVAP valve located on right side in engine compartment above wheel.
    Look for green EVAP test port close to it.
    Toyota Purge Selnoid is made by DENSO.
     
  9. Jul 21, 2022 at 5:58 PM
    #9
    CodeSeven

    CodeSeven LOC: 33.781461, -115.867251

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    There might be a sensor near the VSV. It's a vacuum sensor making sure that the intake is vacuuming air from the emissions system. I have it on the v6, not sure if your 2.7 will have it. The part # for mine is 89460-04010. It doesn't look like your 2.7 uses this one but there might be one similar. There are some ohm tests you can do that will tell you if this is the problem. you'll have to find all the resources for a 2.7 though, all mine are 3.4

    https://www.tacomaworld.com/threads/fuel-tank-pressure-sensor-as125-89460-04010.452808/
     
  10. Jul 22, 2022 at 8:07 AM
    #10
    tirediron

    tirediron Well-Known Member

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    Almost any Launch or Autel unit with bi-directional capability will do the job, but you're going to spend north of $750, which buys you a lot of diagnostic time at a shop...
     
  11. Jul 22, 2022 at 10:02 PM
    #11
    Pakuadragon

    Pakuadragon Active Member

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    I've had this same issue for close to 3 years. I've change out the VSV for a known good sensor, changed the fuel sender unit gasket, and made my own smoke machine. None of which have worked. Next step is to replace all the evap hoses. Hope you get it figured out, as it will likely help me out as well. I have had to keep erasing my codes and driving for at least 75 miles in order to pass my smog.
     
  12. Jul 22, 2022 at 10:15 PM
    #12
    2ndtaco4me

    2ndtaco4me Well-Known Member

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    Dang, replacing the charcoal canister worked for me. Same code on the '02.
     
  13. Jul 28, 2022 at 7:54 AM
    #13
    chrskpln

    chrskpln [OP] Active Member

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    UPDATE: I tried replacing the Purge Solenoid @Black DOG Lila. I cleared the codes and have driven 50 miles with no light so far. Pending codes popped up (p0442 and p0446). I'm not sure if that's because the computer hasn't registered a repair yet or if it's because I haven't repaired the issue. At any rate, I'm sure the light will have the opportunity to come on today as I will be doing much driving.

    If this isn't the solution, than I guess I need to replace all the hoses as @Pakuadragon recommended. @CodeSeven, My mechanic said my fuel tank pressure sensor was reading right, but if that was the problem, wouldn't it spit out a p0452?

    Thank you all for helping me out here. I'll update on whether the problem has been resolved or not. Also, more ideas are welcome.
     
  14. Aug 1, 2022 at 8:22 AM
    #14
    chrskpln

    chrskpln [OP] Active Member

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    UPDATE:
    P0442
    P0446

    These two came on after 102 miles and I have the p0440 pending. The EVAP monitor hasn’t completed just yet since I cleared the DTCs.

    Are there any other VSVs? I was under the impression there were three for the EVAP system.
     
  15. Aug 1, 2022 at 10:21 AM
    #15
    chrskpln

    chrskpln [OP] Active Member

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    So I was looking under the hood and noticed that there is no hose going from the CCV to the air filter. Instead, the hose is connected to the throttle body. Could this be setting off the codes?
     
  16. Aug 1, 2022 at 3:01 PM
    #16
    kgw

    kgw Well-Known Member

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    Have you checked your vacuum at the manifold? The V6 has a port on the front of the manifold with a cap on it: I connect my vacuum gauge to it...Hopefully the 4-banger has such a thing. New gas cap, new oil cap for the valve cover...Fix all the hoses.!!! I was failing tailpipe emissions. Hoses get old and stiff, and then they split. Too much air entering behind the MAF will get 'ya.
     
  17. Aug 2, 2022 at 7:51 AM
    #17
    chrskpln

    chrskpln [OP] Active Member

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    Here is a picture of what the engine bay is supposed to look like. I highlighted the CCV VSV.

    3769CD11-82A9-4291-921E-E1C5C230945D.jpg
     
  18. Aug 2, 2022 at 7:53 AM
    #18
    chrskpln

    chrskpln [OP] Active Member

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    Here is a picture with my own engine bay. As you can see, there is no hose connecting the CCV to the air intake. I ordered the right hose and a valve port cover for where the hose is connected now. Does anyone think this could be the root of the issue?

    6C18519D-5CF9-40ED-BCB6-F7F9E469AD6B.jpg
     
  19. Aug 2, 2022 at 9:18 AM
    #19
    copycat

    copycat Member

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    I had a similar EVAP problem with my '04. Perhaps this diagram may help. The one CCV hose goes to the air intake manifold and the other should go to the throttle body. The hose was in the correct location

    upload_2022-8-2_16-7-19.jpg

    upload_2022-8-2_16-32-9.jpg
     
    Last edited: Aug 2, 2022
  20. Aug 2, 2022 at 11:35 AM
    #20
    chrskpln

    chrskpln [OP] Active Member

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    That diagram shows different than the one for my Tacoma. Here’s what I’m working from:

    FDE07FCD-4820-42EE-8313-8AD3368916C2.jpg
     

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