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Thread: P2096 is being persistent. (Downstream O2 sensor)

  1. #51
    Senior Member klroger's Avatar
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    Quote Originally Posted by Cani Lupine View Post
    Though the thing that I can't understand about that is the downstream sensor reads consistently rich, so if it was getting excess oxygen, wouldn't the voltage be low?
    Yes, the voltage would be low. How are you determining it's Rich when the code is for a lean condition???


    I didn't know what to do, so I didn't do anything

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  2. #52
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    I actually did not know or remember what a catalyst outputs, so I just looked it up. It outputs carbon dioxide and water.

    So I think - estimate, (meaning I don't KNOW the absolute fact of the matter (I think it is important to understand what a person knows and what they think)) that under normal operating conditions the rear O2 sensor should be detecting a rich condition. Such would indicate the catalyst is doing what it is supposed to do. Where within 0V and 5V that rich signal is, I don't have the foggiest.

    I don't KNOW what voltage reading indicates lean / rich. But it would seem to me that the "all is normal" reading of that rear O2 sensor should be "rich." Maybe it is reading "too" rich. Or maybe the sensor that was installed was in some way, not the correct sensor.

    Lean = Less fuel / More oxygen required for a stoich combustion.
    Rich = More fuel / Less oxygen required for a stoich combustion.

    In the case of a catalyst, the catalyst should output little or no oxygen, it is just CO2 and H2O. Which would equate to Rich in my description above.

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  3. #53
    Senior Member Cani Lupine's Avatar
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    Quote Originally Posted by klroger View Post
    Yes, the voltage would be low. How are you determining it's Rich when the code is for a lean condition???
    I'm using an UltraGauge to watch the upstream lambda and downstream voltage.

    The upstream lambda consistently stays around .93-98 during average driving, which indicates a slight rich mixture, and the downstream voltage hangs around .75ish volts, which is also a bit rich. Of course, there is fluctuation, but they both stay on the rich side the majority of the time.

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  4. #54
    Senior Member klroger's Avatar
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    Quote Originally Posted by Cani Lupine View Post
    I'm using an UltraGauge to watch the upstream lambda and downstream voltage.
    Sorry, I'm going to have to ask what "Lambda" is.. I don't know fancy words.., Why would you use different words or measurements for 2 same sensors??? Are the 2 signals the same if you look at them in a graph??? Sorry, but I'm really now confused... But it doesn't take much to make me confused...
    I didn't know what to do, so I didn't do anything

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        click to view fuel log View my fuel log 2018 Mirage GT 1.2 automatic: 37.3 mpg (US) ... 15.9 km/L ... 6.3 L/100 km ... 44.8 mpg (Imp)


  5. #55
    Senior Member Cani Lupine's Avatar
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    Quote Originally Posted by klroger View Post
    Sorry, I'm going to have to ask what "Lambda" is.. I don't know fancy words.., Why would you use different words or measurements for 2 same sensors??? Are the 2 signals the same if you look at them in a graph??? Sorry, but I'm really now confused... But it doesn't take much to make me confused...
    No worries.

    "Lambda" is a way to measure the air/fuel ratio. A lambda value of 1 means you have just the right amount of air and fuel for complete combustion. Greater than 1 means it's lean, less than 1 means it's rich.

    Wideband O2 sensors are often called lambda sensors or linear sensors, as the signal it gives is directly linear to the air/fuel ratio.

    Narrowband sensors are most common, and they have a very narrow air/fuel ratio range they'll read in near that ideal air/fuel ratio, and give a signal voltage between 0.1 and 0.9 volts. Low voltage means lean, higher voltage means rich.

    Our cars have a wideband sensor upstream, and a narrow band sensor downstream.

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        click to view fuel log View my fuel log 2014 Mirage DE 1.2 manual: 49.2 mpg (US) ... 20.9 km/L ... 4.8 L/100 km ... 59.1 mpg (Imp)


  6. #56
    Senior Member Mitz's Avatar
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    @Cani Lupine

    from the DTC desciption in the FSM, the code is generated if either one of the front or rear sensors is bad. And since both sensors were already replaced, could it be that an injector is at fault?


  7. #57
    Quote Originally Posted by Mitz View Post
    @Cani Lupine

    from the DTC desciption in the FSM, the code is generated if either one of the front or rear sensors is bad. And since both sensors were already replaced, could it be that an injector is at fault?

    Or a bad sensor…again. I just went through a similar thing with a gm. Had a wonky front o2 sensor, replaced it with an ntk o2 and that made it run like crap at random. Installed an oem one and it’s been fine for a week now.

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  8. #58
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    Cani - I admit I don't know much about this whole issue. But according to what I estimate, the rear O2 sensor should detect rich if everything is working as designed. That's what I *think* based on my post #52.

    Based on your original post #1, you say the previous sensor and the new sensor detect lean, resulting in activated the CEL with P2096 (I think is the number you said).

    Perhaps the catalyst has reached the end of useful life? I've never had but just one fail. And it failed from, I don't know, age / crumbling / blocking exhaust flow. That catalyst that failed on me blocked the exhaust enough that much over idle the car had no power and smelled like rotten eggs. But I suppose there are other ways it could fail that I'm not aware of.

    Perhaps there is a way to test a catalyst to determine if it is working as intended?

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        click to view fuel log View my fuel log 2020 Mirage ES 1.2 manual: 42.4 mpg (US) ... 18.0 km/L ... 5.6 L/100 km ... 50.9 mpg (Imp)


  9. #59
    At this point I'd just sell it and buy beer or keep throwing random parts at it then sell it and buy beer.

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        click to view fuel log View my fuel log 2014 Mirage SE wussie cvt edition. 1.2 automatic: 37.7 mpg (US) ... 16.0 km/L ... 6.2 L/100 km ... 45.3 mpg (Imp)


  10. #60
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    Definitely throw parts at it first.

    Quote Originally Posted by 7milesout View Post
    Perhaps there is a way to test a catalyst to determine if it is working as intended?
    I was thinking. Maybe you can get a friend to help you. Have your friend put his face immediately adjacent to the exhaust pipe. Then you crank the car. Have your friend inhale the exhaust. If your friend gets dead really quickly, then I think your cat has failed. If he lives like 15 minutes or longer, your cat is probably good. No wait, maybe that's backward. At any rate, go ahead and do that while we figure out which way means what.


        __________________________________________

        click to view fuel log View my fuel log 2020 Mirage ES 1.2 manual: 42.4 mpg (US) ... 18.0 km/L ... 5.6 L/100 km ... 50.9 mpg (Imp)


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