I’m trying to diagnose a p0125 code on my 99 corolla. Toyota forums seem to say Toyota didn’t follow standards on this code and it is likely also the O2 sensor, can anyone confirm if this is the case?

I’m getting no other codes, and it will run for about 30 minutes before triggering again. Last time it triggered I saw exhaust smoke on the way home, which went away as soon as I reset the code. after clearing the code the exhaust while clear does seem to be rich smelling. Engine seems to run fine, I’m not noticing any performance issues, not signs of dipping oil/coolant amounts. coolant gauge is operating and hitting the halfway point normally.

I can’t think of anything else but the O2 sensor but I expected rougher performance and don’t really want to spend $125 on a part if I don’t have to.

  • venusaur@lemmy.worldEnglish
    0·
    3 days ago

    I have a pretty affordable Foxwell ($50) scanner that shows live data but there are a lot of other options. You could go to an auto store and ask to borrow theirs. You should see both O2 sensor jumping between 0.1 and 1. I’m not a pro though so should probably watch some videos or ask somebody else about how to text the O2.

    Good luck!

    • socphoenix@midwest.socialOPEnglish
      0·
      3 days ago

      I got one from Walmart for $50 that allowed for a phone app to record while I was driving home. Coolant hung from 174-184 (F), and it’s the upstream O2 sensor that is showing issues. Specifically running lean, never getting over .065v and reading 0 several times at idle, which was also about 20 rpm low sitting at roughly 685 instead of 700.

      So googling tells me it could be:

      • Vacuum leak at the throttle body (the common reason)
      • Dirty MAP sensor
      • Old O2 sensor
      • Exhaust leak
      • Weak fuel pump
      • Dirty fuel injection
      • Restricted fuel line

      Only the first 3 really seem likely so I’ll probably start with those and reply to this thread generally once I have a final fix. Thankfully none seem all that major.

      • venusaur@lemmy.worldEnglish
        0·
        3 days ago

        Nice job chasing it down. Hopefully it’s one of those, but either way a learning lesson and fun if you like working on cars

        • socphoenix@midwest.socialOPEnglish
          0·
          3 days ago

          Definitely a learning lesson! I really don’t care for any vehicle work larger/more complicated than my old motorcycles but I also prefer to not pay a mechanic to fix this stuff as often as possible.

          • venusaur@lemmy.worldEnglish
            0·
            3 days ago

            For sure. I imagine working on a bike might be easier in that there’s a lot of open space to get to what you need to?

            • socphoenix@midwest.socialOPEnglish
              0·
              2 days ago

              Usually yes. The bike I work on the most the whole motor falls out the bottom if you remove five bolts so even large overhauls are manageable. Other routine maintenance things are also placed in convenient places.

              The clutch is on the side of the motor (usually the bottom left) and come out with just that cover removed.

              The suspension I replaced without any tools besides a socket wrench as I could put them on the wheel and just lift the wheel by hand to place it correctly onto the other side of the frame.

              • venusaur@lemmy.worldEnglish
                0·
                2 days ago

                That sounds so nice haha. I’ve done some jobs on my cars where removing a single bolt took almost 30 min.