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OBD Scanner O2 sensor questions (P0420)

Discussion in '2nd Gen. Tacomas (2005-2015)' started by ticaz, Aug 5, 2020.

  1. Aug 5, 2020 at 5:53 PM
    #1
    ticaz

    ticaz [OP] Well-Known Member

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    Hello Folks!

    Wondering if anybody out there has the knowledge to help me make heads or tails of this.

    I threw a P0420 code the other day (bank 1 low Cat efficiency). I did some research to try and diagnose bad Cat/vs O2, What I am seeing online is in a normal circumstance, B1S1 jumps around in voltage (for air fuel mix corrections), and B1S2 should hover around .5 volts post Cat. Now, if the Catalytic converter is bad, your B1S2 will jump around as well, as the Cat is not properly "burning off" any contaminants.

    Using the live monitoring on my scan tool I got the following screen shots with both Bank 1 and 2 for comparison (bank 1 should be my trouble maker according to the code).

    This first one is in some stop and go traffic:

    This one is at idle:


    First off, I am confused, as sensor 1 is reading around 3 volts. Is this because its an A/F sensor and not an O2? And I barely see any fluctuation, compared to what I see in "examples" online.

    Secondly, B2S2 seems to be jumping around way more than my "code throwing" B1S2.

    I will likely be bringing it in for an expert diagnosis, but I was just wondering if anybody here could help me make sense of this data.

    Thanks in advance!

    PS, scan tool used is the BlueDriver Scan tool.
     
  2. Jan 27, 2021 at 12:20 PM
    #2
    Mojo Jojo

    Mojo Jojo Well-Known Member

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    Did you ever get this resolved OP? Trying to chase down a PO157 code and came across this thread as I'm thinking of buying the BlueDriver scanner.
     
  3. Jan 27, 2021 at 3:55 PM
    #3
    ticaz

    ticaz [OP] Well-Known Member

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    Yes, It ended up being a leak in the "donut/exhaust gasket" after the header right before the sensor. The gaskets started to disintegrate. Because it was leaking sensor wasn't getting a proper reading. Sensor was fine, when I found the leak, I plugged it with a damp cloth, and the sensor jumped back to normal readings. Replaced the gaskets, and cleared code. No more issues.

    Been super impressed with my scanner, and have used it on a few friends vehicles since.
     
    b_r_o likes this.
  4. Jan 27, 2021 at 4:16 PM
    #4
    Mojo Jojo

    Mojo Jojo Well-Known Member

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    Thanks, good to hear you got it resolved and about the scanner.
     
  5. Jan 27, 2021 at 4:29 PM
    #5
    TnShooter

    TnShooter Well-Known Member

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    What scan tool is this?
    Thanks.
     
  6. Jan 27, 2021 at 6:11 PM
    #6
    ticaz

    ticaz [OP] Well-Known Member

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  7. Jan 27, 2021 at 6:11 PM
    #7
    TnShooter

    TnShooter Well-Known Member

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  8. Jan 27, 2021 at 6:12 PM
    #8
    ticaz

    ticaz [OP] Well-Known Member

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    What do you think is causing your code? Faulty sensor?
     
  9. Jan 27, 2021 at 7:57 PM
    #9
    Mojo Jojo

    Mojo Jojo Well-Known Member

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    I suspect an exhaust leak in the URD Y Pipe I recently put in is allowing air in and creating a false lean reading, which would trigger a low voltage reading (O2 sensor sends 0.1 to 0.9 volt signal, 0.1 is lean and 0.9 is rich)

    The truck only has 17k miles so I dont think it's the sensor. I'd like to test it to be sure but I'm trying to figure out which wires are which (there are 4 wires, 2 for the heater, one for the signal, one for the ground). Still trying to find info on how to test an O2 sensor on a 3rd gen.
     

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