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After driving on the highway, my downstream O2 sensor voltage was a steady 0.8V, which is high.

On the other hand, when idling before the drive, it was a steady 0.3V.

Is it normal for the downstream O2 sensor voltage to be so high after driving? Does this mean I have a bad catalytic converter, or is there another explanation?

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  • How did you get on with the articles? See mechanics.stackexchange.com/q/82358/10976
    – Solar Mike
    Mar 31 at 8:30
  • @SolarMike That question was about the upstream O2 sensor, which Jupiter pointed out was probably actually an A/F sensor. I think he’s right that my upstream sensor is okay, but want to delay accepting his answer until I’m sure. This question is about the downstream sensor, which seems to be a traditional O2 sensor. I’m only asking these questions because my O2 monitors and catalytic converters keep showing “Incomplete” when OBDII-tested, so I suspect there’s a problem among them.
    – Asker
    Mar 31 at 13:07
  • @SolarMike Also, I read a few articles before asking, and they say that a high downstream (post-cat) O2 sensor voltage could mean that my catalytic converter is not working well. I’m just asking to get some second opinions
    – Asker
    Mar 31 at 13:11

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