Hey all I have a CEL on, and this is the code that came up: P0420 - Catalyst System Efficiency Below Threshold Bank 1. I did some searching around and found a few people claiming its either the rear O2 sensor, the front O2 sensor (or A/F sensor??), or the catalytic converter. But on most forum posts I've seen, no one replied back to let people know if replacing em all was successful. Just knowing if anyone has run into this code and successfully fixed it so it didn't come back?
I just got the rear o2 sensor from the dealer and had my buddy mechanic put it in. He reset the comp, and 5 miles down the road the CEL came back on. So I guess next guess is the A/f sensor?
I am saving the catalytic converter for last because that's the one thing that is still under warranty on my car (70k miles). As far as I can tell in the scion manual, the cat is covered til 80k. So I figure if I can replace both the sensors for cheaper than dealer rates, when I bring it in they can't try those and charge me *crosses fingers*.
Anyway, if anyone has input on this... like what I should try, what I shouldn't bother trying I would really appreciate it!!
Oh - back story, last year the CEL came on a few times, but would go off after a few hundred miles, then stay off for like a month or so at a time. I always figured it was my gas cap. But now its been on for longer than normal and I need to get it inspected!!!!! AHHH!
Also-I have no aftermarket parts on it, its all the same car as when I bought it. Mechanically, anyway.