Catalytic Converter, P2195 Conundrum...

Discussion in 'Gen 3 Prius Technical Discussion' started by HerbTheNewPriusOwner, Mar 25, 2020.

  1. HerbTheNewPriusOwner

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    Hello - This is my first Prius and my first post. Unfortunately, it's about a problem. :(

    I 'inherited' a 2011 Prius, 219K miles, from my girlfriend after the head gasket blew. Water ingress into the combustion chambers. I ended up replacing the engine with a 50K mile JDM unit and the thing ran fine, until... the dreaded P2195 DTC. So, here I am, hat in hand asking for y'all's sage advice. The facts of the case are this:

    Pulled the upstream wide band AF sensor (B1S1)
    - It's a Denso part
    - Heater element shows 3ohms cold, 6+ ohms when hit with a blow torch
    - The voltage swings from 0v cold to 3-4+ volts when torched
    - Reaction times seem pretty quick when I put the heat to it then take it off.

    Reinstalled that sensor - still popped a P2195 :(

    So I whipped out the ODBII computer and tracked a few numbers. The ones that caught my attention were the catalytic temperature readings.

    - Cat Temp B1S1 is always 100' higher than B1S2. To me this is backwards.
    - B1S1 output voltage is always above 3V

    Finally, the exhaust smells like rubbing alcohol. Pew!
    [​IMG]

    So what do y'all think? Bad cat? Bad AF Sensor? Bad Both?

    Any advise would be appreciated. These parts are a bit on the pricey side and I don't want to shotgun parts trying to fix the problem.

    I'll tell y;all the whole story of how she did it, what I had to do to 'rescue' her and what the fix ends up being when this is all over - hopefully soon! :D

    Thanks!
     

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    #1 HerbTheNewPriusOwner, Mar 25, 2020
    Last edited: Mar 25, 2020
  2. Peter123

    Peter123 Member

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    Usually a bad cat gives a rotten eggs smell. The temperatures could be backwards, if the front part of the cat is covered in soot. The only cheap fix I can think of comes from decades ago. You take the cat off of the car and soak it in hot water and dish soap overnight. Then rinse it out the next day and put it back on. I never did that, but peeps did swear by it back in the day. There are cleaners that you can put into the fuel and run through the engine and into the cat, but these don't work all that well. The active chemical is usually acetone. You didn't hear it from me, but to be somewhat effective you need to put more in than the EPA approved instructions tell you to use. Or, if you want to take chances, you could put a gallon of acetone into the fuel and go drive the car at high speed and draw down the tank.
     
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  3. PriusCamper

    PriusCamper Senior Member

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    How many miles did replacement engine work normally for before these symptoms?
     
  4. HerbTheNewPriusOwner

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    Not very long. About 50 miles or so before the check engine light came on.

    Peter, we're showing our age. I haven't heard of anybody washing a catalytic converter in over a decade! If you think the cat is the main issue, I'm inclined to invest in a new one. ** This car has turned into the pet project, money pit from hell but to me, it's like adopting a rescue stray you've been fostering for a while. It just grew on me after a few weeks.

    ** Ok had to edit this post. Just watched a video from Scotty Kilmer where he suggests doing that exact thing. Given that the car was driven quite a few miles with radiator coolant infused steam coming out of the exhaust, it may very well be clogged. Hmmm... I got the time. I might try it.
     
    #4 HerbTheNewPriusOwner, Mar 26, 2020
    Last edited by a moderator: Mar 26, 2020
  5. PriusCamper

    PriusCamper Senior Member

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    Well, I'm sure you did some work on the replacement engine to reassure yourself that it was a good engine. So it seems like now is a good time to pick up where you left off on that. The strange exhaust smell is concerning... Perhaps something got damaged when putting the engine in, or perhaps something in the engine was already damaged?

    Please make sure to come back to this thread and let us know what it was once you find out.
     
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  6. HerbTheNewPriusOwner

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    So all's well that ends well ...

    Becoming frustrated with the scan tool's contradictory readings, I decided to take matters into my own hands and go straight to the 'horses rear' and read the cat temperatures directly with an infrared thermometer. My and the mechanic's thermometers agreed, the front of the cats were cooler than the rears by around 100'F, in both cases.

    This new information, while not quite a smoking gun, certainly put the spot light on the front AF O2 sensor (B1S1) as the source of the P2195 problem. So I replaced it. The logic being that if the cats do turn out to be bad, I would go ahead and replace them and the sensors as well. So why not start with the most likely sensor causing the problem.

    And it worked!

    The pending codes were cleared by the scan tool and permanent P2195 error went away after 3 drive cycles and 75 miles of driving around. Plus the rubbing alcohol smell is no longer coming out of the exhaust. Yippee!!

    The engine is fine. In fact, it runs GREAT! Smooth as silk, powerful (for a Prius) and very quiet.

    But the scan tool still reads the cat temps backwards even though the actual temps (under the car) are correct. :confused: Go figure.
     
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