is obd2 code #p0420 cat related or sensor related and i on 2000 Toyota 4Runner

i replaced both 02 sensors about 5 months ago ck eng lite came back on about 1 month ago what now?

Asked by for the 2000 Toyota 4Runner
1 answer
this could be alot of issues but the catt's are 12 yrs old, get a diag and est