I have an Innova 3040C scan tool and a 2013 Hyundai Accent. Under live data I have O2B1S2 which I believe is the downstream O2 sensor. Oddly there is no O2S1B1 listed. There is a LambdaB1S1 voltage reading. I'm trying to track the possible causes of a 420 code. My Lambda reads a consistently high .945 v which occasionally will jump as high as 1.2 and drop as low as .850. It does not cycle as I would expect the upstream O2 to do.

1 Answer 1


Easy to find out: unplug the sensor (electric supply) and see what the scantool tells. If it tells B1S2 you got your answer.

  • Is your sensor warm enough?
  • Does it react (correlate) to changes in throttle position
  • especially cut off?
  • does your throttle(flap) work correctly? (by cable or wire?) clean if neccessary
  • Doh! Great idea. Sensor is warm enough. It does react to throttle but not as I would expect. I was expecting to see the usual rich/lean pulse but I'm not seeing that. STFT seems as expected -3/+3. LTFT is consistently high which is the opposite of what I think I'm seeing with the high O2 reading (rich). I would expect all fuel trims to be in the negative with the O2 showing rich.
    – soulTower
    Jan 30, 2020 at 15:25

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