1. Welcome to Tacoma World!

    You are currently viewing as a guest! To get full-access, you need to register for a FREE account.

    As a registered member, you’ll be able to:
    • Participate in all Tacoma discussion topics
    • Communicate privately with other Tacoma owners from around the world
    • Post your own photos in our Members Gallery
    • Access all special features of the site

EVAP system CEL P0456

Discussion in 'Technical Chat' started by hladun, May 23, 2012.

  1. May 23, 2012 at 8:23 AM
    #1
    hladun

    hladun [OP] Well-Known Member

    Joined:
    May 21, 2012
    Member:
    #79246
    Messages:
    123
    Gender:
    Male
    Alberta
    Vehicle:
    Tacoma
    I've been getting the P0456 code on my 08 Tacoma.

    This is very useful;

    http://www.ncttora.com/fsm/05+/data/ileaf/06toyrm/06toypdf/06rmsrc/rm2006ta/0050037.pdf

    My question is during "Operation C: EVAP pressure Measurement" the pump discharges into the cannister filter. The filter is connected to the tank filler neck below the gas cap so it's connected back to the tank. So how can it draw a vacuum when it's pumping in a loop?

    Thanks.
     
  2. May 31, 2012 at 8:45 AM
    #2
    hladun

    hladun [OP] Well-Known Member

    Joined:
    May 21, 2012
    Member:
    #79246
    Messages:
    123
    Gender:
    Male
    Alberta
    Vehicle:
    Tacoma
    Surprised that no one could answer my question. Fortunately I was able to make a fix that has cleared the code. Put hose clamps on cannister filter hoses.
     
  3. May 31, 2012 at 1:01 PM
    #3
    tan4x4

    tan4x4 Well-Known Member

    Joined:
    Nov 30, 2011
    Member:
    #67982
    Messages:
    3,152
    Gender:
    Male
    First Name:
    Rick
    Folsom, CA
    Vehicle:
    99 Tacoma EC 4x4 2.7L Auto
    Bilsteins, OME 881's, 3-leaf AAL, Detroit TruTrac, 31" tires, Michelin LTX AT2, Tranny skidplate, TC skidplate, CBI rear bumper, TG sliders, UltraGauge, PowerTank, Reverse Camera, CB
    I believe that, normally, the EVAP system carries a vacuum.

    But when the vehicle is first started, a small pump pressurizes the system and checks for a leak (holds the pressure). If a sensor detects a leak-down, it throws the code. If it can't hold a small pressure, then it can't hold the vacuum either.

    At least this is how our 2002 Dodge does it. I had to replace a split vacuum hose when it threw an EVAP code.
     
  4. Jun 2, 2012 at 6:12 PM
    #4
    hladun

    hladun [OP] Well-Known Member

    Joined:
    May 21, 2012
    Member:
    #79246
    Messages:
    123
    Gender:
    Male
    Alberta
    Vehicle:
    Tacoma
    I had a careful look at the filler today and, sure enough, just under the lip on the right side of the filler there's an opening for the vent line. So the vent system does vent to atmosphere.

    Tan4x4 if you read the link in my first post it explains how the system works and not how you have described.
     
  5. Jun 2, 2012 at 6:19 PM
    #5
    98tacoma27

    98tacoma27 is gooder 'en chicken Moderator

    Joined:
    Dec 18, 2008
    Member:
    #11714
    Messages:
    49,887
    Gender:
    Male
    First Name:
    Ben
    Beech Creek
    Vehicle:
    05 Tundra SR5 (+250k AND COUNTING), 88 SR5 PU (SOLD), 98 TRD OR (CRUSHED)
    5100's all on fours
    It's not in a loop. The system is closed.
     
  6. Sep 3, 2012 at 1:26 PM
    #6
    FRYBOTH

    FRYBOTH Well-Known Member

    Joined:
    Aug 30, 2012
    Member:
    #85850
    Messages:
    83
    Gender:
    Male
    First Name:
    Christian
    Seattle
    Vehicle:
    08 Tacoma Base 4x4 2.7L Inline 4
    I got this code as well. My own mechanic skills and tools are rather limited. What is it that you did to fix it? I also have a family member with expert skill when it come to this sort of thing. So whatever you can tell me I can pass along and he can help me do it. Thanks!
     
  7. Sep 4, 2012 at 9:17 AM
    #7
    hladun

    hladun [OP] Well-Known Member

    Joined:
    May 21, 2012
    Member:
    #79246
    Messages:
    123
    Gender:
    Male
    Alberta
    Vehicle:
    Tacoma
    In the end I replaced the charcoal cannister assembly and the code has gone away. When I took the old one apart it appeared that the very tiny vacuum pump was ceased. Reread my other comments and look at the link to understand how the system works. Basically it wakes up in the middle of the night and draws a vacuum to see there are no leaks.
     
  8. May 22, 2013 at 5:28 AM
    #8
    ScissorMeTimbers

    ScissorMeTimbers Crème fraîche.

    Joined:
    Jan 1, 2013
    Member:
    #94156
    Messages:
    120
    Gender:
    Male
    First Name:
    Matt
    Hawaii - Stationed @ Hurlburt Field
    Vehicle:
    08 Black V6 SR5 TRD Off-Road.
    Been getting this code on and off for awhile, now it finally seems that its here to stay. Before I take it to get checked out (hopefully under my extended warranty) I want to try this hose clamp fix. Where are these cannister filter hoses you speak of? Pics? Thanks!
     
  9. May 22, 2013 at 6:35 AM
    #9
    hladun

    hladun [OP] Well-Known Member

    Joined:
    May 21, 2012
    Member:
    #79246
    Messages:
    123
    Gender:
    Male
    Alberta
    Vehicle:
    Tacoma
    While doing a search I came across some old posts by me when I was hunting the P0456 problem. I want to update it so if anyone else is looking they get the right answer. What it did turn out to be was that the diaphragm in the refuelling valve was ruptured. It is a used truck so maybe overfilling the tank by the PO or an accident caused the rupture. Unfortunately the solution was the very expensive charcoal cannister assembly.
     
To Top