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Thread: Replace Front O2 sensor to fix code P0031

  1. #1

    Cool Replace Front O2 sensor to fix code P0031

    ---> Hydrolix suggested a write up on this, so I went back and took some pics when i did my oil change / tire rotation.

    //

    DTC P0031 — HO2S HEATER CONTROL CIRCUIT LOW (BANK 1 SENSOR 1)

    I was showing the P0031 code with a CEL. I reset it twice but it came back almost immediately upon start up.

    i OHM'd out the 2 black wires on the O2 plug side - and got nothing (the multi-meter stayed at 1) - I read that it should have between 4-6 ohm's of resistance.

    so it would appear that the sensor needs replaced.

    This is the front O2 sensor I got from AAP. Denso is the OEM part maker too. FWIW.

    denso @ 188.99
    http://shop.advanceautoparts.com/web...RPEMISAMS_____

    -----

    Changing out the sensor is pretty straight forward.

    **** If you have the chance i suggest soaking the old sensor with PB- blaster the night before.

    **** rent the 7/8 (22mm) crows foot o2 removal tool from Adv. Auto.
    It looks something like this:

    The straight version doesn't allow for clearance with the car chassis.

    1. remove passenger tire
    2. remove splash guard access window
    3. remove air box (this will allow access to the valve cover where a bracket is located that holds the sensor wires our of the way.)
    4. unplug 02 sensor (by passenger front shock tower)
    5. unbolt bracket by coil plug (12mm)
    6. remove 02 sensor from header

    tire is on, but you can see the access window.


    panel removed showing sensor in header (right before up-pipe)


    the top plug is the o2 plug.




    this is the WRONG 02 socket to use


    it places the extension/ratchet in the way of the chassis.


    Sorry I don't have more pics, but its not that hard. Get the offset removal tool, soak overnight, and it should go pretty easily.

    --

    reinstall in the reverse order.(use copper anit-seize on threads.)

    reset check engine light and enjoy.

    Facebook changed how they host pics, so I've relinked them. (4.26.14)
    Last edited by turbo sol; 04-26-2014 at 06:27 PM.

  2. #2
    Where'd the pictures go? My car just threw this code a couple of days ago...

  3. #3
    FWIW I got the denso o2 from advance for 80 bucks with coupons. Replacement is pretty darn easy with the car jacked up, wheel off and working from the wheel well.
    -Greg
    2004 FXT 5MT

  4. #4
    pics relinked. good luck, it's pretty simple to do.

  5. #5
    Thanks for reposting the pics. Looks like the price has gone up a little (~$20, but I usually get some AAP coupons in the mail. I'll repost when I've knocked it out.

  6. #6
    UPDATE - If you're like me and you drive a unicorn (stock '02 bugeye), you may find that the exhaust shield port is too small for the socket or the offset wrench.
    IMG_6670.jpg

    My Father-in-law & I had to notch it out and then it came right out. Also, disconnecting the battery will reset the Check engine light ~ if you don't feel like driving for 45 minutes.
    IMG_6664.jpg

  7. #7
    Scoobie Expert page2334's Avatar
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    A 7/8 wrench works also
    2006 Subaru Impreza WRX STi Superleggera

    [email protected]!! ya dont have to trap high to run fast
    [ KCSR Subaru STI's own all SQUAD ] #1
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  8. #8
    Also, after you disconnect the battery, push the brake pedal. Then wait 5 minutes. That will reset the CEL.


    Subaru, it's all we'll drive!

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