P0420 Bad o2?

[harriman]

Is it possilbe that a faulty o2 sensor is causing a P0420 code? If i were to replace the O2 sensors and indeed do have a bad CAT can i cause harm to my O2 sensors?

thanks
-harri

[Kraln]

It depends. The 1995 only has one o2 sensor, and that's pre-cat. I think the later models have one pre- and post-.

Of course, it really can't hurt to swap it out, a new o2 sensor is like $70, where as a new cat is $$$$.

[harriman]

Thanks,
Yeah I have two o2 sensors. I was getting the CAT efficiency code so I replace it with a non oem cat, as well as replacing both o2 sensors. Now this non oem cat is going bad (rattle rattle) and I'm wondering if my OEM cat was ok. and i was just getting this error due to bad o2 sensors.. what do you guys think? I feel like I would get a bad 02 sensor code if they were bad. Maybe they were just on their way out?