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rear o2 sensor - DONE!

Discussion in '1st Gen. Tacomas (1995-2004)' started by bowyer2002, Feb 26, 2011.

  1. Jan 14, 2014 at 7:50 PM
    #61
    Farmboy

    Farmboy Member

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    Mike
    western MA
    Vehicle:
    2002 Tacoma 2.7L 4x4
    windshield compass haha
    I just started this project on my 02 Taco. What I learned is that the size of the nuts shrink from corrosion damage, so you need a range of socket and wrench sizes. For socket you need a set of deep ones to remove the heat shield (held on by 2 nuts) probably between 9 and 13mm (mine was 10); you will need a low profile socket wrench. As for the nuts that hold the 02 sensor in....well, mine was corroded down to almost 9mm...I hear it is supposed to be 13, we'll see when I finally get the #$#!er off. I took the shield (around the o2 sensor) off with a sawsall as well, to see if I could get more of a grip on the nuts from that side. I tried using everything including vise grips. I did not wait at all to start wrenching after using PB blaster, so I did not get anywhere...I'll try again tomorrow and heat the area up by driving around. The vise grips got a promising bite on the nuts, but failed at first try. If it doesn't work tomorrow, I'll try getting a stuck nut remover set like Bowyer did (with success). The guy at the shop told me if neither of us can get these stupid nuts off, I will have to get a whole new muffler and exhaust pipe as well..........I said, "give me the keys." Now look what I got myself into. May as well save me from buying a cat this year if my issue is only this stupid sensor (known defective). Add that to the cost of the new exhaust and labor....you get the picture. I'm getting these freakin nuts off if it's the last of me.
     
  2. Jan 15, 2014 at 3:26 PM
    #62
    budget76

    budget76 Active Member

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    Mike
    New Jersey
    Vehicle:
    98 xt-cab 4x4 4cl/2.7 stock man
    soon want dual lockers Picture was my 85 dual arb great
    i SOLVED THE PROBLEM BY BUYING A CAT-BACK MUFFLER
    AND TAIL PIPE IN ONE PIECE FOR $139 DELIVERED TO MY HOUSE. tHEN ANOTHER 40-45$ FOR THE o2 sensor. jUST CUT THE OLD BOLTS OFF WITH THE SAWS-ALL or 4.5 inch grinder, I forget. Took 30 minutes for all. Now I am good for another 150,000 miles before doing that crap again. Will probable need a new CAT but that will be again simple grinding and cutting two bolts.
    Good luck.
     
  3. Jan 16, 2014 at 3:00 PM
    #63
    Farmboy

    Farmboy Member

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    Mike
    western MA
    Vehicle:
    2002 Tacoma 2.7L 4x4
    windshield compass haha
    I just found out you can add 1 gallon of pure laquer thinner to your gas tank when half full, then drive at 2500 RPMS for 30 mins (at neutral) or 150 miles drive time. This is a good way to clean out the cat, and may turn off the check engine light and solve the problem....supposedly your 02 sensors can detect a mere 5% efficiency loss from the cat and you end up thinking that it is time to buy a new cat. You can also completely remove cat (somewhat difficult and definitely annoying job) and soak in laundry detergent and water for 24 hours. Of course, first a bench test should be done to the o2 sensors with a multimeter and a PROPANE (only propane) torch. Pull sensor from car. Connect black probe to ground wire or (in some cases) the case of the sensor is negative. Positive goes to positive. Multimeter set on voltage. Use propane torch to briefly heat sensor tip to red hot then remove heat immediately,...heat again until red hot and remove heat...continue this process watching the mulltimeter. It will take 2 or three times to get the sensor up to 600 degrees where it will start to give feedback to the multimeter. You should see voltage rise to 1 volt and rapidly go to zero when heat is off. If you get any other reading: your o2 sensor is either failing or already dead.
     
  4. Feb 10, 2014 at 6:11 PM
    #64
    icecoldramfan

    icecoldramfan New Member

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    One thing I found out is to carefully take off the rocker panel to access the o2 sensor connection. Cut my heat shield then bent it back to get to the nuts. Then bent it back and used jb weld to reinstall. Luckily the truck spent most of its life in southern cal so nuts weren't too bad. Replacement nuts were $7 from dealer.
     
  5. Apr 12, 2014 at 7:00 AM
    #65
    nickaz30

    nickaz30 west by god

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    trd sport
    volant goodyear duratracks,,,,,2.5 leveling kit/ 1.5 aal....six shooter wheels
    Cool...I just let the dealer try to change my P2197 sensors...they stripped the threads and had to get me a new exhaust manifold and converter....but it was free!...
     
  6. Oct 8, 2014 at 12:17 PM
    #66
    YLit

    YLit New Member

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    virginia
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    HOW to replace rasted stads that holds rear O2 sensor?
     
  7. Dec 18, 2014 at 12:37 PM
    #67
    RustedTaco

    RustedTaco New Member

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    Free! To replace the manifold and converter??!!

    My dealership is warning me that they might strip the threads and that it will cost me $1700 to replace if they do!!

    I'm going out to buy some PB Blaster and pre-soak the threads before I take it in to get the O2 and mass airflow sensor replaced.
     
  8. Nov 4, 2015 at 3:21 AM
    #68
    layback

    layback New Member

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    Check "Amazon.com" but call the Toyota Parts Department for the part numbers, you can cross reference the number for a compatible one at a better price.
     
  9. Dec 20, 2015 at 1:27 PM
    #69
    dpenfield1

    dpenfield1 Member

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    dave
    orange, ca
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    1999 tacoma 4wd sr5 v6
    How many total O2 censors are there on 99 Tacoma?
     
  10. Dec 16, 2017 at 4:15 PM
    #70
    Suki-2

    Suki-2 New Member

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    Where can you buy the shield?
     
  11. Dec 16, 2017 at 5:04 PM
    #71
    ToyotaJim

    ToyotaJim Well-Known Member

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    +1 A nut was so stuck on mine that it took the bolt out with it..
     
  12. Dec 16, 2017 at 5:05 PM
    #72
    ToyotaJim

    ToyotaJim Well-Known Member

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    There are 2, both are accessible from underneath the truck
     
  13. Dec 17, 2017 at 11:37 AM
    #73
    Suki-2

    Suki-2 New Member

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    I cut the shield and took my battery pliers and took the nuts off.
    The pliers get a good grip and it's a piece of cake believe or not.
     
  14. May 26, 2018 at 1:33 PM
    #74
    surlyrgr

    surlyrgr Member

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    backed into a tree
    I would have saved myself some time if I had seen your post sooner. I also removed my heat shield. I popped the welds with hammer and chisel. Those are some substantial little tack welds. The nuts should have been 12mm though. At least mine were on the front sensor and I'm assuming they were the same on the rear. Mine were rounded from corrosion. Once I got the shield out of the way, I tapped my cheapest 11mm socket on and had them off in five minutes. I am going to replace all four nuts with stainless as I've seen suggested here by someone else who ran into this problem.
     
  15. Mar 17, 2019 at 8:16 PM
    #75
    pontoon

    pontoon Well-Known Member

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    I did the upstream O2 sensor today. I found the nut and the stud had welded together. When I took off the nut, the stud was left with very little threads--badly damaged. I was able to bolt the new O2 sensor on with a new nut, but I'm concerned about this setup. Is it possible to replace the stud (seems unlikely as it looks welded on). Is it possible to repair the stud? I want to avoid buying a new cat if I can.
     
  16. Mar 17, 2019 at 8:47 PM
    #76
    Currygoat

    Currygoat Well-Known Member

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    Rims, 4600 Bilsteins, K&N filter
    I think they sell the OEM studs. I somewhat remember seeing them as a part number when I replaced my 02 sensor last year. They may screw in??? If so you can take them off and reinstall them with the "two nut" trick: go to 16:51 https://www.youtube.com/watch?v=nFYEoWTX0YU
     
    pontoon likes this.
  17. Jul 12, 2019 at 9:56 AM
    #77
    Tman93

    Tman93 Member

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    Cold air
    Hey all, very informative thread just curious I have the extended cab in the pics it shows where the sensor is under the floor mat, just curious would this be by my back seats or in the front? I would assume the back. And how did you get the black gromit thing back on the wire? :confused:
     
  18. Aug 7, 2019 at 5:57 AM
    #78
    srhorn

    srhorn New Member

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    The connection is under the carpet just behind the front passenger seat. You have to remove the door sill to lift up the carpet. The new Denso sensor comes with a new grommet, so no need to use the old one.
     
  19. Aug 23, 2019 at 4:31 PM
    #79
    Fly Guy

    Fly Guy Well-Known Member

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    Eastern Shore of MD ... for now
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    More than some ... Less than others
    Just did this with my Son's 1st Gen with 191K. Replaced the Up Stream without issue. Came apart easily and back together quickly ... maybe 30 minutes total.

    The Down Stream sensor and all the help here made it much easier. Sprayed penetrating oil on the studs for the last three days. Removed the heat shield and started trying to figure out what size socket to use. Well, turns out that I didn't need a socket at all ... Maryland road salt, brine and rust had totally removed the nuts. I pulled the O2 sensor out, by hand, without much effort and the "Shield" still looks brand new. Had to use a Die to restore the threads from the shear amount of rust and crap embedded on the studs. Added two SS lock washers, nuts and Anti-sieze and no CEL for 30+ miles. Fingers crossed it stays out!
     
    c0climber likes this.
  20. Aug 11, 2020 at 12:58 PM
    #80
    dcubed

    dcubed Well-Known Member

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    Instead of starting yet another thread on this topic, I will just add my $0.02 on the matter of replacing the rear O2 sensor (between cat and intermediate/muffler pipe). My '03 had the small shield intact. Being a New England truck, the nuts were corroded *almost* to the point of being gone. Though I was able to pick off most of the remaining nut material with a pointed chisel, I had insufficient access to remove enough of the nuts to get the sensor out.

    Not wanting to cut the shield, I dropped the intermediate pipe. I used an angle grinder to cut off the flange bolts then pulled off the three rubber hangers from the muffler pipes. With the front of the pipe on the ground (and the rear draped over the rear axle), I was able to chisel away the remaining nuts in two minutes to remove the O2 sensor. I cleaned up the O2 port hole, the two flange surfaces, replaced all the hardware with stainless, replaced the flange gasket and replaced the O2 sensor and gasket.

    It sucks that Toyota uses crappy steel on the nuts to hold what is clearly known to be a maintenance item, pretty much mandating an extra one to two hours on a fifteen minute job.

    stainless hardware used:
    O2 sensor: M8 x 1.25 nuts (with flat and lock washers)
    flange hardware: M10 x 1.5, 40 mm long (with flat and lock washers)
     
    Last edited: Sep 13, 2020

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