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anyone having/had this issue??

Discussion in '1st Gen. Tacomas (1995-2004)' started by nutter, Jul 6, 2010.

  1. Jul 6, 2010 at 3:00 PM
    #1
    nutter

    nutter [OP] Member

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    My check engine light has been on in my 98 Taco 2.7 4x4 for a while. I ran diagnostics on it and it came back with a faulty AIT sesor. I followed the advice from a couple people on here and cleaned it along with the throttle body. Needless to say this not only cleared the code for that problem, it made my truck run better than it has in a long time. Well, on my way to work after clearing the code, I get the notorious CEL again. Run diagnostics on it and it comes back with "CAT running bellow threshhold", the guy that ran it says its either the O2 sensors or the cat itselft. The O2 sensors were just replaced last year and the cat was change about 4 years ago. Is it possible that becuase the AIT/MAF sensors were gunked up causing the truck to run rich that it ruined the O2 sensors? Or can they be cleaned?
     
  2. Jul 6, 2010 at 3:01 PM
    #2
    chris4x4

    chris4x4 With sufficient thrust, pigs fly just fine. Moderator

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    It could have taken out the O2. You cant clean them.
     
  3. Jul 6, 2010 at 3:20 PM
    #3
    nutter

    nutter [OP] Member

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    Is there a way to make sure? I dont want to spend money on O2 sensors that I dont need and it end up being the cat.
     
  4. Jul 6, 2010 at 3:28 PM
    #4
    Coolidge

    Coolidge Well-Known Member

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    Glad to hear the cleaning (kinda) worked for you. The problem was, you drove it with the light on for awhile. Def could be the sensors. I cleaned mine within a hour of the CEL coming on. The truck has never run better since I bought it, and CEL hasnt come back on. Good luck with your sensors. Do 'em soon so they dont screw up another emission control part. Good Luck
     
  5. Jul 6, 2010 at 4:08 PM
    #5
    nutter

    nutter [OP] Member

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    ya im going to double check volts on them with a scan tool just to make sure its them and not the cat. I'm leaning towards the O2's though. Thanks guys
     
  6. Jul 6, 2010 at 6:31 PM
    #6
    skytower

    skytower Well-Known Member

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    Too rich for too long will burn up a cat too.
    Start with the cheap easy checks first.
     
  7. Jul 6, 2010 at 6:56 PM
    #7
    biggdog747

    biggdog747 Well-Known Member

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    try not looking at the votages but at the wave forms of b1s1 b1s2 if the are the same the cat is bad but if b1s1 goes up and down and b1s2 is flat line then the cat is good. i would say that it kicked that code because you cleaned everything. clear the code and run it. i may not come back on. it is a two trip code which means you need two drive cycles for the code to come back on.
     
  8. Jul 7, 2010 at 1:12 AM
    #8
    nutter

    nutter [OP] Member

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    i cleared the code and the cel came back on after about 55miles so, I will disconect the battery again and see if/when it comes back on. I am going to have access to the scan tool thursday so I shall see.

    thanks
     
  9. Jul 9, 2010 at 1:48 PM
    #9
    nutter

    nutter [OP] Member

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    Ok I scanned the O2 sensors and they are supposed to be running at .1-.9 volts when warmed up. Both were running at .08-.09 at times. However 1/1 was always the highest, most of the time. 1/2 would jump up higher than 1/1 at times. Im going to replace them and see if it fixes the problem.
     
  10. Jul 9, 2010 at 9:03 PM
    #10
    Gwest1967

    Gwest1967 Active Member

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    See if you can get a muffler shop to run a check on the cat, they drill small holes in the pipe in front and back of the cat, and put in a sensor to see if the pressure is the same.. I got it done for free, found out the o2/fuel ratio sensor was bad.. Be careful with buying after market sensors too, the toyota computers throw codes that are decieving..
     
  11. Jul 10, 2010 at 12:02 AM
    #11
    skytower

    skytower Well-Known Member

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    If the sensors are working correctly, the pre-cat sensor should fluctuate and the post-cat sensor should stay the same(with a good cat). If the cat is bad, both sensors will fluctuate.
    Sensors are cheaper than a cat. Pressure readings will only tell you if the cat is falling apart and blocking the flow. Get a tail pipe reading of emissions. That will give you a good indication of cat health.
     
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