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Thread: help with oxygen sensor reading

  1. #1
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    help with oxygen sensor reading

    Need help with O2 sensor readings.

    I have LS400 2000 model which has 4 Oxygen Sensors.
    I think that i may have some problem in my O2 sensors.
    if you guys could check this readings and help me with this issue & tell me if these sensors are either functioning correctly or not.

    These are readings of O2 sensor on idle without acceleration.


    These are readings of O2 sensor with accelerate up to 2000 rpm.


    These are readings of O2 sensor back on idle without acceleration.


    These are readings of O2 sensor again with accelerate up to 2000 rpm.


    These are readings of O2 sensor back finally on idle without acceleration.


    Help!

  2. #2
    Variable Bitrate
    Join Date
    Oct 2008
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    Seem to be missing some data.
    First graph with the engine idling is perfect.
    2nd graph the only problem I see is Bank 1 sensor 2 giving a low signal.
    Front sensors says there not a lot of oxygen when it's high. Rear sensor constantly says there's a lot of oxygen in the gas. Either sensor defect, wiring problem, heater problem or a leak in the catalyst where oxygen can enter into the gasses.
    Bank 2 seems to be reacting as expected when the catalyst is cold that is. Otherwise this catalyst is deteriorated a lot.
    The only other thing is that when accelerating the oxygen sensors are quite slow. But that could be another problem causing this.

    Do you have DTC's set? If so, which one(s)?
    What are the complaints? High fuel usage? Engine hesitating?

  3. #3
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    p2psmurf,
    Thanks for your reply...
    I do not have any DTC ,

    the only problem is that
    fuel mileage is low which is 19 - 20 MPG on highway compared with other LS400 owners who get 24-30 MPG on highway.
    I have changed spark plugs, cleaned engine air filter. But i think it may be because of these O2 sensors.

    Bank 1 sensor 2 readings are not similar to Bank 2 sensor 2 readings, does this means that i had to replace the sensor. Or what if the problem from the CAT, to inspect this could i swap both of these sensors and check readings again?

  4. #4
    Variable Bitrate
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    What are the values in live data for Fuel system an Long Term Fuel trims?

    Have you checked the tab Trouble codes? Because the monitors for the Oxygen sensors and Oxygen heaters are not complete. Usually that means a DTC. Could be in mode 7 still and not a DTC which sets the MIL yet.

  5. #5
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    Fuel system data


    Live data at idle without acceleration


    Live data with acceleration on 2000 rpm


    DTC at mode 7 , no pending DTC


    Monitored Test Results


    I don't know about these readings, could you tell me in case if any of these readings are wrong..

    waiting for your reply..

  6. #6
    Variable Bitrate
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    I see 2 things.
    1. Basic fuel is 9% too lean on both banks and corrected by the Long Term Fuel trim.
    2. Inlet Air temperature is very, very, very high. 67 degrees Celsius is just way too much.

    Check airmass sensor with a full throttle run. Only log pid 10 Air flow rate and find the highest value.
    Check Intake Air Temperature after normal driving. Should be way less than what you have now.

  7. #7
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    Here is data again taken after a normal drive.


    http://img227.imageshack.us/img227/5479/firstd.png
    -

    http://img826.imageshack.us/img826/6500/second.png

    What do you recommend/suggest ?

  8. #8
    Variable Bitrate
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    I see 2 things.
    1. Basic fuel is 5% too lean on both banks and corrected by the Long Term Fuel trim.
    2. Inlet Air temperature is very, very, very high. 55 degrees Celsius is just way too much.

    Long Term Fuel trim reduced from 9 to approx. 5 for both banks. Check all hoses and pipes around inlet manifold for a small air leak.

    Intake Temperature is still very high. If the outside temperature is more than 45 degrees Celsius than it makes sense. Otherwise either the air is heated some way or the sensor is just giving a wrong signal. Check Intake air temperature with a thermometer or read out temperatures after overnight stop. Water and Air should then be equal to the outside temperature.

  9. #9
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    what you think the reason behind too lean fuel on both banks?

    Do you mean EVAP hoses/pipes which are connected to manifold and air cleaner intake?

    Coolant fluid level is below low. Does that also effect on Intake air temperature?

  10. #10
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    These reading on cold start after overnight stop. Outside temperature is 36C
    http://img831.imageshack.us/img831/9...rtreadings.png


    waiting for your reply..

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