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Thread: Running rich issue

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    Running rich issue

    Hi guys, just replaced my 02 sensors, went for a drive and the engine management light comes on, hook up the scan system with live data, and it's reading Bank 1 /Sensor 1 as having a fault, "Oxygen sensor heater"

    Is it possible for a new sensor I've just replaced to be defective already? Or is there some sort of reset I needed to do for all the sensors at once. I replaced all 4, because I got them at a good price. They were all denso or blueprint OE quality. No fault codes for the other three.

    Few pictures of the live data, it may mean more to you than it does to me.

    http://uploads.im/4BNbL.jpg

    http://uploads.im/fFVp1.jpg

    http://uploads.im/xXtBI.jpg

    http://uploads.im/v94cK.jpg



    http://uploads.im/uPB4k.jpg

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    elnevio's Avatar

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    I'm guessing it is a late facelift V6?
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    Confused's Avatar

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    The cheapest way to check would probably be to move that sensor to another location, and see if the fault follows the sensor, or stays in the same location (which could indicate a wiring fault).

    Once you've confirmed that the sensor is awry, any reputable supplier should replace the sensor for you. If the fault doesn't follow the sensor, then you know the sensors are all OK, and can begin tracing back from the plug on the heater circuit and see where is is failing.

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    Yes it's a facelift 2001 V6 Galant Estate.

    In response to the heater circuit you mentioned Confused, am I correct in assuming whatever sources the Oxygen sensor heater power is fused specifically? I've checked the wiring and it's all pretty good, as you will know, the sensor coming off bank one, closest to the top of the rad, has a short length wiring connection to the plug, which then follows along another loom. Nothing was really moved in that general area.

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    Confused's Avatar

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    In the 2001 service manual supplement, it shows the following, which may (or may not) be an issue...

    o2-1.PNG

    It shows a difference in heater circuit resistances between front and rear banks - and ASA shows that each of the 4 sensors has a different part number (MR507749, MR507750, MR507751 and MR507752) - I wouldn't have thought that they would do that if they were the same...


    Anyway, here's the troubleshooting steps, which tells you which pins to check for what voltages and resistances.

    o2-2.PNG

    The same page for the rear sensors shows a different resistance range (11-18Ω) - it does say "measure at the harness" so it might be car-side, rather than sensor side.


    I hope this helps

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    I would have thought measure from the harness would be measure on the wiring loom in the car after disconnecting the sensor.
    This is very good you to go to all the trouble of finding the information and explaining it Gary.
    You da man.

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    Yeh thanks a lot for the info, I replaced the sensor and it's still pulling a code for the same oxygen sensor, as well as a code for short term fuel trim and excessive time to enter closed loop, it's now misfiring under load but idles perfectly whilst standing still, I'm at a loss now. At my wits end with this...

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    elnevio's Avatar

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    Might be worth employing the services of a local auto-electrician? Arm them with the info in this thread as well, but their experience may make a big difference. Could be £50/60 or so but there may be something else that pops up that they can identify quite easily.

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    Nick Mann's Avatar

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    Misfiring under load is likely to be ignition more than fuelling isn't it? Under closed loop the lambda sensor won't be having an input to the ecu?

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    Well I popped another sensor off my old Galant (2002) and it still pulls a code for bank one sensor one, checked all the wiring and its fine. I did have a code pop up briefly for the ignition timing and misfire detected on cylinder five, which I'm assuming is on bank one at the front of the engine where it's pulling the code for bank one sensor one, but that went away. Did a little research at the time and it could be linked to a faulty ignition coil or HT leads.... but.... even if I fix the misfire issue, the sensor issue more than likely will be prevailent.

    Nick Mann I thought the Lamda sensor didn't have any input until the sensors were warm and engine has reached conditions to take it out of open loop. I was under the impression closed loop were fuelling specifications adjusted and maintained purely by upstream and downstream oxygen sensors and the MAF.

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    Sorry, I have written it down wrong. The lambda sensors will absolutely have a say in closed loop. I meant to say open loop. I was trying to make the point that under load the car is likely to be in open loop and ignoring the lambda. But then I wrote closed instead of open and just confused everyone. Including me!

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    Still having issues with this, still idling perfectly, whilst I can take the revs up to 6000 slowly without a hitch or fast without a hitch. Had an auto electrician in who said that the sensor is getting power where it needs through its heating stage and power when it needs it. But the sensor isn't switching like the others it just stays at 0.2mV or whatever the unit of measurement was.

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