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Actron OBD11 scanner HELP! PO420 code

Discussion in '2nd Gen. Tacomas (2005-2015)' started by Bradyfb, Jun 19, 2014.

  1. Jun 19, 2014 at 4:06 PM
    #1
    Bradyfb

    Bradyfb [OP] New Member

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    Brady
    wv
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    02 SR5
    I have the po420 code on my SR5 V6 and i have a (Actron OBD11 scanner plus). and I would like to fix the problem, i would also like to learn more about troubleshooting with this actron scanner. I'm looking at O2S11 (v) 3.265 and O2S12 (v) .455;
    Now I'm wondering how to interpret these readings to a bad cat or a bad o2 sensor... Knowing that the O2 sensors change resistance with change in temp. With what I've read the readings should be within a .5v of each other. What part of the picture am I missing?
     
    Last edited: Jun 19, 2014
  2. Jan 13, 2015 at 1:50 PM
    #2
    Jake in Manassas

    Jake in Manassas Member

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    Jake
    Manassas
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    2009 Tacoma 299,598 miles on 12/28/2014
    Just for anyone who may still be following....I believe I have resolved everything. Keep in mind, I have an 09 TRD with 300K miles, and have been riding for many miles now with a code reader connected. This code reader has the capability to display pending codes before the go permanent (shows engine light on dash), has a readiness test to show all tests pass, fail, or incomplete for Emissions, and display live data. I had all sorts of codes flying Mass air sensor, catalysts too low in bank 1 po420, 2 po424 and final. also p440. I first replaced MAF sensor, did not work. I started using fuel system cleaner since the fuel filter is internal to th tank as a part of fuel pump assembly. This helped quite a bit especially with the catlyst bank 2. I changed my PCV Valve helped even more. I replaced the gas cap, and I believe this also helped for passing the EVAP test. I started to realize that all of these issues seemed to be a part of combustion air flow drop, yet I change my air filters every time I change my oil. BUT, BIG BUT, on at least the TRD types, the breather has a flow straightner (or final filter, I think a straightner because I am a controls guy for my career) after the disposable air filter itself. It was frustrating that this filter/straightner doesn't seem to be able to be removed, so I sprayed it with some carb cleaner. Amazing results, but still occasional Air flow code, and PO420 catalyst too low bank 1. I took the breather off, and almost emptied a can of Carb cleaner on both the exposed side and into the opening where it attaches to air valve. even shook the fluid around by shaking the breather body. NO MORE MAF code even as a pending code. Keep in mind that before a code hits your dash, it will be in pending code for a while both time, cycle, and miles. Plus it is the yests that make you pass the emissions test. In fact, I have a green light for passing all the tests including O2 sensors and EVAP test complete, yet the catalyst too low was still throwing a code. Also, the EVAP test takes a considerable amount of miles, time and on/off cycles to complete. I would only erase codes once the went from pending to stored, since every time you erase codes, all the tests reset, and the EVAP one takes a long time. Well the bottom line here is that with restricted combustion air flow, anything that uses vacuum (EVAP) will give you a problem if your Combustion air is restricted since it is this air that creates the vacuum. Also, if starving for air, any other O2 sensor or catalysts codes can be affected. The only code I get now (and sometimes resets itself to okay before going to a stored code) is PO420 Catalyst too low bank one. Well the only way any of these Catalyst codes are developed are from the O2 sensors. one on each ex manifold and after the Catalytic converter. I have the new O2 sensors, waiting for the weather to be okay for the replacement, since I can see that my bank one sensor's value when reading live occasionally goes negative. I hope this helps anyone else. it just goes to show you that sometimes its not just replacing parts, and you have to look at the entire system. For instance, you could also have a bad spark plug cause an O2 sensor code. Anyway still going strong with engine running like new, as well as fuel economy at 301,858 miles. Oh, and the guy that said the metal flapper on fuel tank neck is important to the EVAP system is wrong. just look at the little hole tap that is above the flapper which is where the EVAP is pulling the evaporation of gas fumes from, and the flapper would need some sort of seal to make it bubble tight. The flapper is a check valve/backflow preventor safety so if you leave your gas cap off, and start driving the gas wont fly out. But I agree, over filling your tank could do damage to your EVAP system, which I never do anyway, since you can now have liquid gas get sucked into the evap system rather than just fumes. I am concerned about this now since my flapper check valve is missing. Good Luck. I know I'll pass my inspection coming in March at 300K +!!!
     
  3. Jan 15, 2015 at 12:15 PM
    #3
    Jake in Manassas

    Jake in Manassas Member

    Joined:
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    2009 Tacoma 299,598 miles on 12/28/2014

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