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Thread: Rear 02 sensor error

  1. #1

    Rear 02 sensor error

    Hi guys.
    '06 XB9SX, 80000km.
    On my way home last night , and again on my way to work this morning, the CEL came on for
    about 5 km, then went off. Bueltooth showed a stored rear 02 sensor error. Is this likely
    a component failure in process, or should I be looking at a possible wiring issue ?
    Thanks.

  2. #2
    Senior Member Barrett's Avatar
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    Quote Originally Posted by Beebop View Post
    Hi guys.
    '06 XB9SX, 80000km.
    On my way home last night , and again on my way to work this morning, the CEL came on for
    about 5 km, then went off. Bueltooth showed a stored rear 02 sensor error. Is this likely
    a component failure in process, or should I be looking at a possible wiring issue ?
    Thanks.
    Is this likely
    a component failure in process


    Possible...but not always.

    The ECM is seeing sensor values it doesn't like....hence the intermittent CEL.
    1-Wildly fluctuating engine temp signal being sent to ECM can cause this. Check ETS connector for condition and ETS harness for chafing. Historically, a known problem.
    2-Ground is being interrupted somewhere. Check them all and in particular, the ECM grounds.
    3-You FAILED to mention rideability issues, or lack thereof. If active CEL immediately preceded by cooling fan activation...it is always a failed ECM ground.
    4-This condition is typically NOT a failing O2 sensor or intake seals. NO mention of AFV value during this horrific experience. TPS reset 10% of the time will resolve this. Worth mentioning.

  3. #3
    Thanks Barrett.
    If I didnt see the CEL , I wouldnt have known it happened, so no performance issues of any sort.
    My AFV has always been within 10% of 100, but I did not check that specifically, will do so if
    it happens again. I did have the ground under the seat off earlier this week, I will check if that
    maybe is an issue.
    Cheers

  4. #4
    Senior Member Barrett's Avatar
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    My pleasure. And think about running a single dedicated ground wire from the rear-most coil bracket mounting bolt to the negative battery cable attachment point on the subframe.....NOT to the negative battery terminal. 16-20 gauge works fine. Often times solves these dilemmas and rideability/ECM issues.

  5. #5
    Well I didnt get a chance to check yesterday, but the trip home gave no CEL.
    Hopefully the weekend will give me more time.

  6. #6
    ok so this morning I made some time to look at it.
    Pulled the entire airbox, checked cables for chafing , reseated everything
    I could access. Added a ground to the rear coilpack mount.
    Hooked up the Buelltooth and this is the readings.
    Oh and while I was at it, I did a TPS reset.
    Attached Images Attached Images

  7. #7
    Senior Member Cooter's Avatar
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    All I can see is that the AFV reading is telling the ECM to pull almost 20%(!!) of fuel from the entire map. An old or lazy O2 sensor can cause that (but that is a guess, not a diagnosis). You can check O2 running voltages under live data.

    The bike will run better if you re-set AFV to 100 and set the AFV limits to 90-110. Its not a "fix" though.

    If it's cheap enough for you to guess, the O2 is behind the cooling fan. Hang the rear of the bike, take off the seat, rear shock, and fan (the bottom slides towards you first and then out the bottom). It is possible to slip a 7/8" wrench under the frame to remove the O2, but a dedicated socket or crowsfoot on an extension is easier.

  8. #8
    Well the only thing I've noticed is a slight exhaust blow between the headers and the pipe. I'll tackle that the weekend and
    reset the AVF to 100 and see where it ends up. I can swing a spanner, but when it come to tuning and electronic brains, I
    get into deep waters. I appreciate everyone's assistance and patience.
    I do have my wife's 05 model which I can swap parts with if I need to , but access to the sensor makes that option
    lower down the list of things I want to do.
    Cheers

  9. #9
    And just to post a follow up, The bike was unused for a month or so while I hacked the pipe and made
    it into a Buell race pipe replica, and also did some cosmetic work. I fixed the slight blow it had where the headers
    meet the main exhaust, double checked the grounds, check for chaffing etc, and have been using it for a
    few weeks to commute. It runs great , sounds great and I have had no issues.....well until yesterday.
    My son, I and a few friends went for a quick 200km breakfast run.
    The outbound trip was uneventful. On the return, I decided to open it up a bit and get rid of the cobwebs. Just as the
    needle hit 200kmph, the CEL came on and the engine lost some power. I eased it off till about 140, and then the CEL
    cleared and it ran fine. The remainder of the way home, as soon as I exceeded around 4500rpm (140kmph), the CEL would
    come on with a loss of power. The power loss doesnt always happen with the CEL coming on though.
    I rode home at a sedate 130, and immediately connected the Buelltooth.
    My AFR was a very acceptable 96,2, and there were 13 incidents of rear 02 inactive. This is currently my only
    mode of transport, so I used it again to work this morning , and I had one occasion where the CEL came on, but no
    performance issues.
    So I'm at the stage where the sensor is looking like the place to start with a replacement.
    Are there any basic tests which can be done on it, or do I just replace and see what it does ?
    Also are there any alternatives available ?
    Thanks again for the valuable support offered here.

  10. #10
    Senior Member Cooter's Avatar
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    It's showing like there's a problem in the O2 circuit. Not necessarily a bad sensor, but the ECM thinks theres something wrong in the circuit.

    It's acting like the fuel system is weak, clogged, or the internal hose has pinholes in it.



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