Air Fuel Ratio Sensor - Possible Coolant Contamination?

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by The Critic, Apr 11, 2019.

  1. The Critic

    The Critic Resident Critic

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    Last night, I changed the air fuel ratio sensor on my 2011.

    This vehicle experienced a head gasket failure approximately 2400 miles ago. The head gasket was repaired properly and there have been no misfires or loss of coolant since the repair.

    I am wondering if the “white crusty stuff” on the sensor below is from antifreeze contamination. The car was driven for less than 50 miles with the head gasket failure and the total coolant consumption was less than a pint. But I would have also expected the “crust” to be pink/red (color of the coolant), not white.

    Thoughts?

    [​IMG]
     
    #1 The Critic, Apr 11, 2019
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  2. audiodave

    audiodave Active Member

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    #2 audiodave, Apr 11, 2019
  3. Mendel Leisk

    Mendel Leisk Senior Member

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    #3 Mendel Leisk, Apr 11, 2019
  4. toplinetax

    toplinetax Junior Member

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    Here is an out of box idea. Scrape off the bits and dilute with fresh motor oil. Let it dissolve and send it to Blackstone for analysis. Since the oil is fresh, whatever is crusted on that sensor should show up. I would think that the concentration level would be off the charts with fresh oil. (n)
     
    #4 toplinetax, Jul 4, 2019
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  5. The Critic

    The Critic Resident Critic

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    Not a bad idea.

    I did recently get a UOA on the car everything turned out normal, so I am hoping that this matter is behind me for a while:

    2011 Prius, Idemitsu ZEPRO Adv. Moly 0W-20, 3,210 miles - Bob Is The Oil Guy
     
    #5 The Critic, Jul 4, 2019
  6. wheezyglider

    wheezyglider Active Member

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    Just by the way - were you able to tell if that sensor was bad? Was there a chronically high long term fuel trim or something before the swap?
     
    #6 wheezyglider, Jul 5, 2019
  7. The Critic

    The Critic Resident Critic

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    I wasn't sure what the substance was, but it is definitely not normal. Since sensors cannot be cleaned I elected to replace the sensor.
     
    #7 The Critic, Jul 8, 2019
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  8. wheezyglider

    wheezyglider Active Member

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    OK gotcha. I've seen some things on how to use scantool data to see if an air/fuel sensor is working (at all), but nothing that would distinguish a good one from an alive-but-dirty one.
     
    #8 wheezyglider, Jul 9, 2019
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