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Which O2 sensor needs replacing?!

Discussion in '1st Gen. Tacomas (1995-2004)' started by athensaustrian, Jul 29, 2008.

  1. Jul 29, 2008 at 3:30 PM
    #1
    athensaustrian

    athensaustrian [OP] New Member

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    Atlanta, GA
    Vehicle:
    98 Tacoma 2WD Manual
    I'm new here, but I have a question that may cost me a lot! I have a '98 Tacoma 2WD manual, and got CEL some time ago. I moved to Atlanta and now have to have emissions inspections. I have not noticed any problems with the vehicle at all (conditions-wise), but got codes P0171 and P0420. Tried to have the guys at AutoZone to help, but I got responses varying from "replace the before cat o2 sensor", to "it's the MAF" to "it's the catalytic converter". I seriously got all different answers from 10 different people. Anybody know definatively what is the answer?
     
  2. May 24, 2009 at 11:26 AM
    #2
    KenpachiZaraki

    KenpachiZaraki Its Wicked Flow BITCHES!!

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    Alex •﹏•
    Lubbock
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    05 TRD OffRoad Poser ψ(`∇´)ψ
    ALL POSER- Afe Pro Dry S drop in filter, 3" AP leaf pack, Eibach w/5100's up front, 5100's rear, Fog Light Mod, ABS off mod, Dash Light MOD, Doug Thorley Long Tube Headers, Wicked Flow Bitches MAX Muffler, 4" floods, 20", 43" light bars, 265/75/16 Hankook Dynapro ATm, oil catch can, rear diff breather relocate, Custome Sliders, SOS concepts Front bumper, Demon Eye Mod, backlit TRD emblem on bumper, Morimoto D2S projectors,
    Working at Autozone, I can tell you that they could print out the trouble code for you, BUT it lists several causes, usually 4 the first usually being the one to fix. So if they told you it could be this, no this, no that, it may be a combination of one or all of the above. If you really wanted to know what it could be, get a diagnostic on it. Sure its about 80 bucks, but at least you'll you what is wrong. Thats what i tell my customers, I never tell them oh its this. Just a little FYI.
     
  3. May 24, 2009 at 11:32 AM
    #3
    chris4x4

    chris4x4 With sufficient thrust, pigs fly just fine. Staff Member

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    FlimFlubberJAM
    Tenoe, AZ
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    The P0171 code most likely means the MAF is dirty, and can be fixed by cleaning it.
    The P0420 Code lists These as possible triggers:
    Leaded fuel was used where unleaded was called for
    An oxygen sensor is not reading (functioning) properly
    The engine coolant temperature sensor is not working properly
    Damaged or leaking exhaust manifold / catalytic converter / exhaust pipe
    Retarded spark timing
    The oxygen sensors in front and behind the converter are reporting too similar of readings
    And these as possible fixes:
    Check for exhaust leaks at the manifold, pipes, catalytic converter. Repair as required.
    Use a scope to diagnose the oxygen sensor operation (Tip: The oxygen sensor in front of the catalytic converter normally has a fluctuating waveform. The waveform of the sensor behind the converter should be more steady).
    Inspect the downstream heated oxygen sensor (HO2), replace if necessary
    Replace the catalytic converter
     
  4. May 24, 2009 at 11:32 AM
    #4
    chris4x4

    chris4x4 With sufficient thrust, pigs fly just fine. Staff Member

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    FlimFlubberJAM
    Tenoe, AZ
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    2013 Rubicon Unlimited,
    4.10 gears, sliders, and lots of buttons.
    Oh...Welcome to TW! :)
     
  5. May 24, 2009 at 1:47 PM
    #5
    trailinTaco

    trailinTaco Well-Known Member

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    Bel Air, MD
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    2000 Tacoma SR5 TRD 3.4L 4x4
    3 inch suspension lift, 33 inch bfgoodrich mud terrain tires, toytech diff drop, Procomp alloy wheels, hella fog lights, black projector headlights with 8000k HID's, blacked out tail lights, two 12 inch subs, 20% tint, pioneer head unit and speakers
    i originally had the p0420 code and then later i had a code for running lean. i ended up replacing the upstream 1/1 o2 sensor and that fixed it.
     
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