ODB II Code 0420 - Catalyst System Efficiency Below Threshold (Bank 1)

I got this code for the past 6 months. I have a code reader so I just clear it. I searched the web and I think it comes from either the O2 sensor or catalytic converter, maybe both. I was wondering if anyone had the same problem and had it corrected?? Any reply will be appreciated. I have a 2001 SE 3.1 w/100,00 miles.

Thanks
Gil

U really need a scanner to hookup to make sure the rear O2 is putting out readings but it would point to bad catalytic convertor.

i agree, it also could be a leak from the 02 senc.