Help with P0420

Discussion in 'Gen 2 Prius Main Forum' started by Frontporch, Oct 26, 2020.

  1. Frontporch

    Frontporch Member

    Joined:
    Dec 18, 2015
    107
    26
    0
    Location:
    Nj
    Vehicle:
    2007 Prius
    Model:
    N/A
    Hello,

    Was about to take my Prius for inspection in NJ after replacing the three way valve (sorry if that's not the name) that routes coolant. I had a check engine light on for over 6 months, but in NJ, you have to remove that even if not emissions related. Replaced the part, cleared the code... after driving a little while ... new code P0420. Darn.

    My Prius has 210K miles... I know that's a lot, but it is not an oil burner. Before doing anything drastic I would like to check some of the basics, like cleaning the MAF, verifying O2 sensor readings and anything else the forum members would suggest. I don't have a lot of diagnostic tools, but I do have a cell phone, an OBDII reader and the Torque app.

    So first off, probably everythings original in the exhaust. Cat failure at 210K common?

    Any suggestions going forward?

    My next plan is to clean the MAF and keep driving.

    Thanks!
     
  2. TMR-JWAP

    TMR-JWAP Senior Member

    Joined:
    Aug 12, 2016
    3,468
    3,930
    0
    Location:
    Columbia, SC
    Vehicle:
    2007 Prius
    Model:
    Touring
    You can purchase a complete bolt in replacement on ebay for less than 400 dollars. I can put you in contact with a scrap dealer in texas that will buy your old cats for significantly more than that. You end up making money and have a new cat system.
     
  3. Frontporch

    Frontporch Member

    Joined:
    Dec 18, 2015
    107
    26
    0
    Location:
    Nj
    Vehicle:
    2007 Prius
    Model:
    N/A
    That's interesting. I know the replacements don't have as much or the same catalyst. Kind of makes sense that maybe I don't need another 200K miles on a replacement. I have been burned by replacements. I put one in my Accord years ago that was a name brand and the CEL persisted. Could have been due to some other factor.

    I am going to keep your idea in mind and consider that if I can't get through inspection some other way. For now I sprayed the MAF sensor and am going to see if that helps.

    I did noticed on torque that there was only one O2 sensor reading. I should have two on a prius right? one forward and one rearward of the cat?
     
  4. Frontporch

    Frontporch Member

    Joined:
    Dec 18, 2015
    107
    26
    0
    Location:
    Nj
    Vehicle:
    2007 Prius
    Model:
    N/A
    I am using the torque app that can show 8 o2 sensor readings. Only one, O2 1x2, has a reading. The reading for O2 1x1 is empty. Is that the upstream sensor? Also the OBDII monitor for O2 Sensor is marked as incomplete
     
  5. mr_guy_mann

    mr_guy_mann Member

    Joined:
    Sep 3, 2020
    150
    68
    0
    Location:
    NJ-USA
    Vehicle:
    2006 Prius
    Model:
    Four
    I haven't tried Torque on a Prius so I don't know how it would display the upstream "oxygen" sensor (B1S1) .It's really an air-fuel sensor (or wide band oxygen sensor) and many "generic OBD2" scanners or apps don't handle it properly. Most Toyota compatible scantools display it as a voltage signal of around 3.3V - the voltage will vary with normal operation. It goes up when the mixture is lean, and down when rich. I usually see 3.2 to 3.4V at idle and 2.5 to 3.8 or so when driving.

    Other scantool might display the air fuel sensor as a milliAmp current value that reads somewhere between - 1.00 to +1.00 mA at idle with larger changes during hard accel or decel.

    If you have problems with the B1S1 reading then just look at fuel trims. Short term fuel trim varies with the B1S1 output but is typically near 0 +/- 2%. If it has to make a larger correction (away from zero) then long term fuel trim will make an adjustment to bring short term back. Short term plus long term equals total fuel trim. The few Prii I have seen have total trims of 5% or less. Anything within +/-10% wouldn't cause me concern.

    The B1S2 is a normal oxygen sensor so it will read 0 to 1V. Normally at a steady highway cruise with a good cat I see around 0.7V with minor flucuations.

    Posted via the PriusChat mobile app.
     
    #5 mr_guy_mann, Oct 27, 2020
    Last edited: Oct 27, 2020
  6. dolj

    dolj Senior Member

    Joined:
    May 14, 2012
    4,916
    2,645
    0
    Location:
    Wellington, New Zealand
    Vehicle:
    2006 Prius
    If you are using Torque and not Torque Pro, spend the $5 dollars and get Torque Pro. Then install the Prius specific PIDs that come with Torque Pro. See what you see then.
     
  7. Frontporch

    Frontporch Member

    Joined:
    Dec 18, 2015
    107
    26
    0
    Location:
    Nj
    Vehicle:
    2007 Prius
    Model:
    N/A
    Thanks for that advice. I have an older copy of Pro on a tablet. Going to connect that and measure O2 and fuel trims and post those here.
     
  8. TMR-JWAP

    TMR-JWAP Senior Member

    Joined:
    Aug 12, 2016
    3,468
    3,930
    0
    Location:
    Columbia, SC
    Vehicle:
    2007 Prius
    Model:
    Touring
    Keep in mind, your Gen 2 catalytic converters are a target. It's not 'if you get hit', it's 'when you get hit'. We're starting to see thefts in the southeast now. In NJ, you're on borowed time. Your choices are to either wait until it's stolen and then eat a big repair bill, or change it yourself and you get to make the money on the deal instead of a thief. With an aftermarket cat, your car will be left alone.
     
  9. Frontporch

    Frontporch Member

    Joined:
    Dec 18, 2015
    107
    26
    0
    Location:
    Nj
    Vehicle:
    2007 Prius
    Model:
    N/A
    I took a drive with Torque Pro and the O2 sensors appeared to be in the ranges mentioned, with one small exception. The front sensor looked like it snapped to 5.0v on release of the throttle, and then went back to normal values.

    I did notice that the final O2 sensor monitor completed and the check engine light disappeared. I was able to take it to inspection where it passed. two more years to not have to worry. Fuel economy is reasonable 45-48 but not incredible. battery voltages appears to be even across all the cells... seem to max out around 17+ V.

    I would like to know more about the catalytic converter issues. Is there something special about the Prius compared to other vehicles or is any car or truck in the last 30 years with factory exhaust a candidate for theft. I have a 99 Ford ranger with California emissions and that would be a lot easier to get under.

    I have also noticed there is a manufacturer that sells metal plates to cover your exhaust and keep thieves away. I wonder what the NJ inspection with their cameras under the vehicle would think about those.

    Thanks
     
  10. mr_guy_mann

    mr_guy_mann Member

    Joined:
    Sep 3, 2020
    150
    68
    0
    Location:
    NJ-USA
    Vehicle:
    2006 Prius
    Model:
    Four
    5.0V for the B1S1 on decel is normal. I said before that voltage goes up when the engine is lean. I forgot to mention that on decel the ecm cuts fuel completely, so the sensor goes to its maximum lean range.

    The OE Prius cat has fairly high amounts of precious metals in order to meet PZEV emissions standards-- even though the engine isn't running all the time. The price of platinum and palladium are way up recently. And the the cat on a Prius can be cut off in a minute or two. So the Prius is a target.

    I looked at one of those security shields for my car and supposedly it has a strategically placed cutout so that visual inspections can be done.

    Posted via the PriusChat mobile app.
     
  11. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

    Joined:
    May 12, 2018
    3,784
    3,719
    1
    Location:
    Pennsylvania
    Vehicle:
    2018 Prius c
    Model:
    Two
    It's relatively big, and has a lot of the money metals in it compared to anything else on the street. Way better payday-per-attack than any other car.

    Why risk jacking 7 Rangers when you can do one old Prius? Less to haul in the getaway car, they can go back to their villainous lair earlier and spend even more time planning smaller candy sizes for next Halloween.
     
Loading...