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P0420 Code comes and goes?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Sande11, Aug 6, 2014.

  1. Sande11

    Sande11 New Member

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    I have a 2007 Prius/70,000 miles and live in NY. The Malfunction Indicator Lamp (Check Engine Light) came on back in May when I was visiting Texas and I stopped to have the code read and got a P0420 code - possible emission problem. As I was far from home I took a day to think about what I should do and by the next evening the light had shut off. Driving back to NY the following week the light came on again about 150 miles from home. Once again within a few days it had shut off. End of June I had the same thing happen - this time I took it to a Auto Part store and had them read the codes again. The guy there told me the only thing that showed up was some kind of emission error. Again within a few days the light went off. Just yesterday (August now) the light came on again. I've resisted taking it to the dealer because I know they will charge me $100+ just to plug it in and tell me what I partly already know. I've been reading up the P0420 code online however still have a few questions.

    A. Is it normal for this code to go on and off repeatedly without me really doing anything?
    B. Is there any way to figure out what the specific issue is without taking it to Toyota?
    C. If it is the catalytic converter would I be covered under the Federal Emission Warranty? - which from what I've read is 8 years/80,000 miles?

    The following is what the initial code printout read:
    Troubleshooting P0420
    OEM Brand: Domestic
    Definition
    Catalyst efficiency low-bank 1
    Explanation
    The oxygen sensors monitor the Catalytic Converters ability to store oxygen.
    Probable cause
    1. Catalytic converter defective (failure possibly due to # 2, 3, or 4)
    2. Engine misfire or running condition
    3. large vacuum leak
    4. Engine oil leakage into exhaust-valve guide seals, piston rings

    Thanks for any advice.
     
    #1 Sande11, Aug 6, 2014
    Last edited: Aug 7, 2014
  2. bisco

    bisco cookie crumbler

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    the o/m should tell you the emissions warranty period.
     
    #2 bisco, Aug 6, 2014
  3. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Yes, the catalytic converter is the likely failed part. It is marginal so the engine ECU sometimes thinks it has failed and sometimes gives it a pass. When the check engine light is on, take the car to your local Toyota dealer so the DTC can be retrieved and the tech can confirm what you have already figured out.

    The cc should be covered under the Federal emissions control warranty, but you should inquire as to why it failed so early and if there is anything you can do to help the replacement to last longer.
     
    #3 Patrick Wong, Aug 6, 2014
  4. Sande11

    Sande11 New Member

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    Thanks for the input! Is it safe to say that because the CEL has been sporadically going on and off (multiple times) it's probably not the O2 sensors? From what I've read O2 sensors could be another possible issue with the P0420 code - however unfortunately I don't believe O2 sensors would be covered under the warranty.
     
    #4 Sande11, Aug 7, 2014
  5. Sande11

    Sande11 New Member

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    I stopped at my local Toyota dealer and they agreed that the issue is most likely the catalytic converter. They agreed to replace it under the Federal Emission Warranty. I was told that while my car milage is relatively low (just below 69,000) they are seeing catalytic converter issues more often due to the increased ethanol in fuel.
     
    #5 Sande11, Aug 7, 2014
    Last edited: Aug 7, 2014
  6. George Suematsu

    George Suematsu Junior Member

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    I had similar symptoms: California 2006, Intermittent P0420 (I bought my own $60 analyzer), 140K, MPG ~38. My dealer replaced the catalytic converter under a 160K warranty. The check engine has gone away and the MPG shot up to 43.
     
    #6 George Suematsu, Oct 12, 2014
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