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.

  • socphoenixOPEnglish
    1·
    2 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
      2·
      2 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

      • socphoenixOPEnglish
        2·
        2 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
          2·
          2 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?

          • socphoenixOPEnglish
            1·
            1 day 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
              2·
              1 day ago

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

              • socphoenixOPEnglish
                2·
                20 hours ago

                So there is an exception to my past statement. Yamahas. The last one I took the engine apart on every bolt was a different damn socket size!

                  • socphoenixOPEnglish
                    1·
                    10 hours ago

                    No clue. Swore I’d never buy another Yamaha…but I failed and have another one. This one I’ve had to do nothing but normal maintenance on and it looks like the same thing. 2 sizes of Allen keys and a socket wrench to remove the plastic fairings just to get to the oil filter for an oil change.

                    I’ve just started to budget for a mechanic doing all the larger maintenance on it this time!