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Any advice on changing the downstream 02 sensor?

Discussion in '1st Gen. Tacomas (1995-2004)' started by veg hed, Apr 20, 2019.

  1. Apr 20, 2019 at 7:25 PM
    #1
    veg hed

    veg hed [OP] Well-Known Member

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    Well, Amazon did it again. I typed in exactly what I wanted and they sent me the wrong part. I should have done a little more research to ensure I got what I wanted.

    Anyway, I thought I ordered the upstream 02 sensor (Denso 234-9001) but I ordered the downstream sensor (Denso 234-4189). I thought no big deal, my truck has 172,000 miles on it so while I'm waiting on the upstream sensor to arrive I'll change the downstream one. It's not that easy.

    I found where it goes into the truck and plugs in under the seat. However, I cannot for the life of me see a way to get to the bolts due to a cover over the sensor. I thought it was a 12mm but maybe it's stripped? And if its stripped or rusted I see no way in getting it off without cutting involved. I searched on youtube and the forum and couldn't find a write up for this particular one.

    Also, is it even necessary to change the downstream sensor?

    Here's a picture of the cover over the sensor.

    IMG_2287.jpg
     
  2. Apr 20, 2019 at 7:29 PM
    #2
    koditten

    koditten Well-Known Member

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    Reserected from the dead.
    Bend it away. If it breaks no biggie. Most don't have that shield anymore.

    Heat the nuts red hot with a propane torch and use channel lock players to remove the rounded off nuts. Take your time. Works every time.
     
  3. Apr 20, 2019 at 7:30 PM
    #3
    thenodnarb

    thenodnarb Well-Known Member

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    1 vote for don't bother. return your part to Amazon. got an Amazon locker nearby? it's easy to return that way.

    i have 325k on my original downstream. apparently downstream sensors last much longer than the upstream.
     
    Area51Runner and veg hed[OP] like this.
  4. Apr 20, 2019 at 7:37 PM
    #4
    Old Swamper

    Old Swamper Tacoma World Poor

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    The nuts are a special nut and soft. They were like $6.00 each. Get 3 Incase you drop one and can’t find it like I did. I changed mine on my 2002 and it wasn’t that hard to do. I don’t recall the shield being a issue but it’s been a couple years since I did it.
     
    veg hed[OP] likes this.
  5. Apr 20, 2019 at 7:40 PM
    #5
    eon_blue

    eon_blue Most Improved Member

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    I cut that little shield with my angle grinder about 3/4 of the way so I could move it aside. Then just bent it back into place
     
    veg hed[OP] likes this.
  6. Apr 20, 2019 at 9:55 PM
    #6
    dweikum

    dweikum Well-Known Member

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    I recently changed mine on my 02, didn't have a problem getting a socket in there and taking the nuts off intact. Guess I was lucky.
     
  7. Apr 20, 2019 at 10:28 PM
    #7
    JJ04TACO

    JJ04TACO Well-Known Member

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    Dude, super easy with a 1/4" or 3/8 stubby ratchet. I think I used a 1/4"... Get a deep socket and slips right over the nuts and off it comes. I had zero issues and bent or destroyed nothing. I hit it with some penetrating oil after a drive and let it cool a bit. I don't even know if that was necessary. Both sensors came right off super easy. I cleaned the gasket mating surfaces and voila.

    As for Amazon, I ordered both sensors and received correct parts...

    Edit, Before unplugging the upstream sensor remove the wiring retainer that holds it to the frame first and pull it down a bit. It's easier that way.

    Sensors are pretty cheap. I did both...
     
  8. Apr 21, 2019 at 12:19 AM
    #8
    sandman8108

    sandman8108 Well-Known Member

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    I just replaced my upstream sensor and decided not to bother with the downstream. Its not giving me any problems, so I figure when it does ill replace it. Why fix something that isn't broken right?
     
  9. Apr 21, 2019 at 12:22 AM
    #9
    eon_blue

    eon_blue Most Improved Member

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    Should only replace it if it's throwing a code, if I remember right the code I got for my rear O2 sensor was a p0136. Replaced the sensor with a new Denso one and it went away
     
  10. Apr 21, 2019 at 12:23 AM
    #10
    sandman8108

    sandman8108 Well-Known Member

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    Thats what I decided to do. Just replaced my upstream after the p1135 code and man my truck runs like its brand new again!
     
    eon_blue[QUOTED] likes this.
  11. Apr 21, 2019 at 12:28 AM
    #11
    eon_blue

    eon_blue Most Improved Member

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    Good to hear, did you go with a Denso sensor? If there's one thing Toyotas are finicky about its sensors...Denso is OEM for Toyota sensors and you hear a lot of issues stemming from people putting in other brands like Bosch and the like
     
  12. Apr 21, 2019 at 12:32 AM
    #12
    sandman8108

    sandman8108 Well-Known Member

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    Ya I went with OEM after reading everybody suggestions. So far so good
     
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  13. Apr 21, 2019 at 1:32 AM
    #13
    Reh5108

    Reh5108 Well-Known Member

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    I forgot I used to have that shield. I remember it being a pita to change the o2 sensor because of it. I just cut it off.
     
    veg hed[OP] likes this.
  14. Apr 21, 2019 at 6:19 AM
    #14
    1997tacomav6

    1997tacomav6 V6 5sp,RegCab,TRD Supercharger,Haltech,meth, 750k

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    I would definitely replace both at the same time. These sensors tell your computer the
    most critical information for your engine to run its best especially if you have a lot of miles
    on them and stay with DENSO.
    They get plugged up with carbon and dirt over time reducing efficiency.

    WD40 and a socket the nuts came right off for me.
     
    JJ04TACO likes this.

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