Cat Error Code?

My girl friends 97 civic lx's engine light came on and the ecu threw the code for a bad cat. It was welded back together recently because it broke off. Is it more likely the cat went bad, or the o2 sensor is broke just asking for an opinion thanks

its the o2 sensor

I have a question related to this thread. I just bought a 95' GSR about 5 months ago and had a freshly rebuilt B18c dropped in it. So I was wondering why my exhaust smells worse than a 1970 Ford van. I ran my trouble codes just yesterday and found out that my VTEC solenoid is bad (which I'm going to replace as soon as possible). But it didn't give me any codes that said my o2 sensor or my cat were bad. Do you think maybe I'm running to lean or too rich? Or should I replace the cat. My car also makes this funny rattling sould whenever I accelerate.

if you threw the catalyst below threshold code (67), then it is most likely your cat. it may also be your o2 sensor, but, if you dont have a code for the o2 sensor (63) or (65), then it is still most likely good.

you said you welded the cat back together? what part of the cat are you talking about..............the flange sides or internally? it is not gutted out? when you put it back on, did you look to see if it was clogged? what is the mileage on the cat?

it was just the catlyst code, and it was the flange side and no i didn't look in side when it was welded back on

well, if you are throwing the catalyst code, your cat has crapped.

you will need a new cat to pass smog. depending on the mileage on the cat, you should be concerned about what caused the cat to crap out in the first place.

It is the cat ,like stated above there is a different code for o2.Carl