I got OBD code: Catalyst system efficiency below threshold.

Is this my O2 sensor or is it the cat?

It's a 96 civic lx.

Help?
ps: search engine is down.

 

you have a bad cat. if you have a code scanner wiith readings. You should be able to see if you o2 is switching. But I think you have a bad cat. Just shake it or hit it with your hand (when cold.) If its good you should not hear anything, and if its bad you will hear it rattle.

 

Any additional opinions? I haven't had time to try looking at the cat. Can I try to reset the CEL and see if it comes up again?

 

Depends...I dont know your mods. Sometimes with an aftermarket highflow cat cars will throw that code because the cat isnt getting hot enough or some rediculous thing. I would first try to replace the 02 sensor, if that doesnt work then go for the cat. You may have just fouled the sensor.