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CEL- An ongoing problem

Discussion in '1st Gen. Tacomas (1995-2004)' started by Cdavis, Oct 28, 2010.

  1. Oct 28, 2010 at 7:15 AM
    #1
    Cdavis

    Cdavis [OP] Active Member

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    OME 2.5" Front, Rear add-a-leaf with extended shackles, Downey Super-clutch, 33" BFG MT
    So back in 2007 I first threw a CEL code p0420 on my 2001 tacoma while living at high altitude and using cheap gas. I was able to get it to go away after clearing it a few times and using a few tanks of high octane gas and lots of seafoam. It has sporadically come back on over the past 3 years, and it seems to only come on after the vehicle sits a while without being driven. In the past few months it has come on twice, same p0420 code each time. I have noticed the "rotten eggs" smell a few times while driving and have been afraid it was the cats (I have the california model unfortunately) since day 1, but I am suspicious since I've been able to get it go to away for long periods of time over the course of 3 years, and haven't really noticed any dramatic performance losses, although my fuel efficiency certainly isn't what it used to be. I just attributed it to the addition of 33's and 2.5 inches of lift though, so it's hard to make a comparison.


    Does it make any sense that my cats could be going bad for years without major issues? It passed emissions tests every year. I have heard it can be the O2 sensors, but again does this pattern of sporadic CEL codes make sense either? I've basically held off on doing anything for some more convincing evidence of what exactly is wrong, however for some reason today I am compelled to figure it out and perhaps try to fix it...
     
  2. Oct 28, 2010 at 7:31 AM
    #2
    tacobox

    tacobox Evasive Maneuvers PMKMS

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    P0420 codes can come and go with no ill effect other than mpg and more emissions. Is this the original cat on your truck? How many miles?
     
  3. Oct 28, 2010 at 7:35 AM
    #3
    Cdavis

    Cdavis [OP] Active Member

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    OME 2.5" Front, Rear add-a-leaf with extended shackles, Downey Super-clutch, 33" BFG MT
    This is the original cat- I'm at 188,000 now, the codes started around 150,000
     
  4. Oct 28, 2010 at 7:36 AM
    #4
    98tacoma27

    98tacoma27 :POOPCORN: Staff Member

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    5100's all on fours
    I agree with tacobox. It can be one of the worst codes to diagnose. It could be anything from an exhaust leak to the cat itself. I would go about it this way:

    1. Check for any exhaust leaks. Fixc as necessary
    2. Replace the AFR (front O2 sensor) with a Denso OEM
    3. Replace the rear O2 with a Denso OEM
    4. Replace CAT

    http://www.ncttora.com/fsm/2003/Repair_Manual/03tacoma/di/eg5vzfe/cip0420.pdf
     
  5. Oct 28, 2010 at 8:30 AM
    #5
    Cdavis

    Cdavis [OP] Active Member

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    OME 2.5" Front, Rear add-a-leaf with extended shackles, Downey Super-clutch, 33" BFG MT
    How ridiculously hard would replacing the cats be for me to do myself without air tools or a torch? Realistically speaking, how much would a shop charge for new cats?
     
  6. Oct 28, 2010 at 8:32 AM
    #6
    98tacoma27

    98tacoma27 :POOPCORN: Staff Member

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    5100's all on fours
    What motor do you have?
     
  7. Oct 28, 2010 at 8:37 AM
    #7
    Cdavis

    Cdavis [OP] Active Member

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    OME 2.5" Front, Rear add-a-leaf with extended shackles, Downey Super-clutch, 33" BFG MT
    the 3.4L v6, and I have the 2 cats, Cali emissions model
     
  8. Oct 28, 2010 at 9:02 AM
    #8
    98tacoma27

    98tacoma27 :POOPCORN: Staff Member

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    05 Tundra SR5, 88 SR5 PU, 98 TRD OR (CRUSHED)
    5100's all on fours
    There are 5 nuts the hold them one; 3 in the front and 2 after the last cat. This doesn't include the senors nuts. A non Cali emissions has two cats also. The difference is what O2 sensors they use (and a couple other things). It would be relatively easy to swap yourself with basic tools. It all depends on if the nuts are rusted fast to the studs.

    http://www.ncttora.com/fsm/2003/Repair_Manual/03tacoma/ec5vzfe/twccsy/comp.pdf
     
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