Cat problem?

[panteramatt]

Had my wifes 97 explorers computer ran since its had a check engine light and it came back as p0420, catalyst efficiency below threshold bank 1. Does this mean the cats are bad or the o2 sensor? Which ones are they? Any fixes?

 

[marragtop]

If the truck is running ok, I'd reset the codes and see if the CEL comes back on. Could be a false reading.