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  1. ALX

    ALX New Member

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    2006 Prius
    154000 miles
    California
    Car runs perfect, 50mpg average

    This is my last week to get the smog done and I can't solve this P0420 mystery
    I'm posting the last P0420 check engine light freeze frame (if I reset it comes back in less than 20 miles)

    Thank you guys....
     

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  2. valde3

    valde3 Senior Member

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    I don’t think anybody will be able to tell from that freeze frame information if it’s catalytic converter or oxygen sensor B1S2.

    You really need to watch live data from the sensors to be sure. And it might not be easy even then. But since you get the code pretty consistently it shouldn’t be impossible to tell. How much oil does your Prius consume?
     
  3. ALX

    ALX New Member

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    Thanks for answering...
    No oil consume / I don't need to add oil between 5000 miles oil changes

    I just got more pics and I'm posting it...
    -Live data stream O2 sensors 1 and 2
    -Engine parameters during Live data stream
     

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  4. JC91006

    JC91006 Senior Member

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    You most likely need a catalytic converter, p0420 is almost always the catalytic.

    Pay your registration fees early so you don't get a penalty.

    You can try cleaning the catalytic or replace with an after market one
     
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  5. ALX

    ALX New Member

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    I just came from a muffler shop and the guy told me it does no exist an aftermarket Prius catalytic converter California legal.
    I really hope he's wrong. I don't want to pay half of my price of my car to have it done in a Toyota dealer.
     
  6. JC91006

    JC91006 Senior Member

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    What city are you in? You would need to know people to get this done
     
  7. ALX

    ALX New Member

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    Riverside, but I'm totally ok to drive some miles to get it done.....
     
  8. 05PreeUs

    05PreeUs Senior Member

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    Your two O2 sensor readings tell OPPOSITE tales....

    The Front (Wide Band) sensor indicates a LEAN condition, while the Rear (Narrow Band) sensor indicates a RICH condition.

    I'm not super familiar with the specific output voltages of the Toyota WB sensors, but all are more volts = more air (lean).

    Since we know no fuel was "added" to the exhaust, it is apparent that the two sensors are not in agreement on what the actual air-fuel ratio is. This is further evidenced by the equivalence ratio and fuel trims which are not the same for the two sensors (if I am reading the scanner's data in chronological order).

    The wide voltage variations of the rear O2 sensor suggest a bad cat, but the higher than normal voltage of the Front O2 sensor and fuel trim, suggests at a minimum, more than one potential issue. With the readings of the Front O2 sensor suspect, it would be unwise to jump to the conclusion of "bad cat".
     
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  9. ALX

    ALX New Member

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    Interesting point of view, but looking the article below, it looks like my Prius A/F is OK between 3 and 3.5V

    The O2 sensor 2 is showing LEAN in throttle

    From Google: The greater the difference, the higher the voltage reading. An oxygen sensor will typically generate up to about 0.9 volts when the fuel mixture is rich and there is little unburned oxygen in the exhaust. When the mixture is lean, the sensor's output voltage will drop down to about 0.1 volts.


    Please let me know if I'm getting something wrong




    It looks like my sensors are showing LEAN and LEAN
     
    #9 ALX, Nov 3, 2016
    Last edited: Nov 3, 2016
  10. ALX

    ALX New Member

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    I just took a look under a Yaris and the front exhaust pipe seems to be the same, or very close to the Prius part.

    Bosal Catalytic Converter
    [​IMG]

    [​IMG]


    Our List Price:$296.53
    Part Number: 18959-05378833


    Unfortunately that part is not CALIFORNIA LEGAL, but it exists an Walker aftermarket Yaris catalytic converter CA legal (not direct fit).

    Would be legal in CA install an Yaris CAT CA LEGAL in a Prius?

    Externally Prius and Yaris have THE SAME 1.5L engine, same 1NZ-FE family
    1NZ-FE Yaris
    1NZ-FXE Prius
     
  11. roflwaffle

    roflwaffle Member

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    I'd take a closer look at the O2 sensors. The front in particular seems to be alternating between a normal'ish range with ~.6V swings, and much smaller ~.2V-.4V swings. The graph of narrow band O2 sensor voltage on this page shows swings that are far more consistent than what your graph shows. The graphs of downstream O2 sensors also look more consistent than what you're seeing, which could be from the upstream sensor going sideways.

    https://www.discountconverter.com/tech-tips/news_page.cfm?Key=catalytic_converter-&News=218

    Also, a new narrow band O2 sensor is a lot less expensive than a new cat. You can get temporary operating permits from the DMV is need be. I think the max is 2 months or so. You can PNO it and get a 1-day moving permit for smog after you fix it. For what it's worth, I have 3 Toyota's with ~700k miles combined and I've never had to replace a cat converter.
     
  12. 05PreeUs

    05PreeUs Senior Member

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    Was specifically referring to WB voltages in my earlier post.

    For reference, typical BOSCH NB O2 sensors respond as ALX suggests.
    [​IMG]
     
  13. Tashfeen Ekram

    Tashfeen Ekram Junior Member

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    ALX,

    How did you end up resolving this issue? I have a similar problem...
     
  14. Dawar nadeem

    Dawar nadeem New Member

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    20190820_122622.jpg P0420.PRIUS 2007 TSPIRIT
    Can anyone tell here which sensor is not good and have to be replaced?
     
  15. Dawar nadeem

    Dawar nadeem New Member

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    View attachment 177675 P0420.PRIUS 2007 TSPIRIT
    Can anyone tell here which sensor is not good and have to be replaced?
     
  16. Skibob

    Skibob Senior Member

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    No. Get techstream and tell us the codes
     
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