Exhaust Removing Rear O2 Sensor

Discussion in '3rd Gen 1997-2002 2.0L SOHC' started by 98_Jim, Jul 24, 2016.

  1. 98_Jim

    98_Jim FEOA Member

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    So I got a P0136 code the other day --- Oxygen O2 Sensor Circuit Low Voltage (Bank 1, Sensor 2). I cleared the code, but it came back a week later.

    A quick look with my scan tool shows that the rear O2 sensor is dead. The output is stuck at 0.00 Volts.

    I crawled under the car and took a look. The wiring is OK but the element part of the sensor is very corroded and it moves if I wiggle it. I could easily break it off completely with my fingers.

    My concern is that it's on top of the exhaust pipe and kind of hard to get at. There doesn't seem to be a way to get an impact gun on it. Has anyone replaced their rear H02S? If so, how did you get it out. Is it easy to remove with a wrench?

    And, where is the connector for the sensor. I traced the wires back from the top of the sensor and they disappear in a wiring harness. Usually sensors have a pigtail with the connector on the end of it.
  2. Gamer92

    Gamer92 FEOA Donator

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    The connector is around the battery and trams tube dipstick. I think it is green.
    Or white

    I used vise grips when ore removed my sensor for the first time. I have a O2 socket but don't think I've used it on the rear sensor.
  3. pcordes1979

    pcordes1979 FEOA Member

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    On my 98 wagon as the rear O2 was being replaced I simply broke off the sensor just leaving the hex part in the cat converter. I then used a deep well 7/8" impact socket with a series of 1/2" extension bars so I could use a breaker bar from above the engine. The extension bars will end up going between the tubes of the intake manifold.

    You can try that method using a regular O2 sensor socket, but due to the cutout in them may make them slip due to flexing from that cutout.
  4. rbailin

    rbailin FEOA Member

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    The O2 connector is identical to the green/white one for the front O2 sensor. You have to remove the battery and battery tray to get to it. There's also a clip a few inches left of the connector that has to be undone. Spray the 4 tray bolts and the O2 sensor threads a few days before the job to give yourself a fighting chance.

    Check that there's no sideways movement at all in the pipe welded to the back of the cat converter where that O2 sensor attaches. If there is, the pipe may break off when you try to unscrew the sensor even if you use an impact wrench. Remove the cat instead (need a muffler shop to burn out and replace the 2 bolts) and put the pipe end in a padded vise to provide backup when removing the sensor.
  5. 98_Jim

    98_Jim FEOA Member

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    Wow.. Great answers guys.. I'm glad I asked here :)
  6. denisond3

    denisond3 Moderator Staff Member

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    My method to prevent exhaust bolts from having to be burnt out - is to use stainless steel bolts (but NOT stainless nuts). I put an antiseize compound on the threads when I assemble the two parts of the exhaust system. Then I put an extra nut or two onto the exposed threads. These nuts are also slathered with any antiseize compound. Covering up the threads prevents them from rusting. Years later, just unscrew the extra nuts, and the remaining nut; no hassle. If you can find 'cap nuts' (also known as acorn nuts) its even better.
    The reason not to use stainless steel nuts with stainless steel bolts, is that stainless alloys can make their way into each others crystalline structure - and create a bond that wont unscrew.
  7. copcarguy

    copcarguy FEOA Member

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    +1
    I recently had to remove my battery tray for the first time for a different repair. I liberally sprayed the 4 bolts, and even so the two closest to the drivers side scared me as I attempted to remove them. They screw directly into the body of the vehicle, and didn't want to release their nearly 20 year old grip.
    denisond3 likes this.
  8. denisond3

    denisond3 Moderator Staff Member

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    I am familiar with that problem. Im not familiar with any easy way to deal with it. I had to drill out the front most of the bolts on one of my Escorts. With another Escort I havent gotten around to getting a drill to where the rear bolt snapped off.
  9. DangerRanger

    DangerRanger FEOA Member

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    The rear oxygen sensor if you notice is in position to get at quite easily with a regular 7/8 box wrench. Problem is you cant get the plug from the wires through the wrench. I made a simple box wrench work by taking a 7/8 box wrench ( cheap one ) and cutting a slot right in the end big enough to get the wires through. Then welded a couple pieces of metal on the end across from each other so I could put a screw across the end to help hold it together under torque. I was trying to make another ( cheap 7/8 wrench ) and grinding a spot on the inside of the box end near the handle just enough to get the plug through as it almost makes it already. That way I don't cut it all the way through and dont have to weld anything.
  10. goltho

    goltho FEOA Member

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    Replaced my rear sensor today, thanks to last year's rabbit apparently having had O2 desserts after its EGR main. This presumably had something to do with the P0316. Chopped what was left of the wires at the sensor end & extracted it with vice grips easily.

    I hate goddam critters. :mad:

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