P0420 1996 Honda Civic -

Question

I got this probable causes
1.- A/F ratio concerns
2.-Air leak near HO2S
3.-Ignition system concerns
4.-faulty catalytic converter
Would you think that replacing the HO2S sensor could be de fix or the TWC

Answer 1

P0420 Catalytic below threshold

All those concern are valid, what you have P0420 is definetly the catalytic convertor that has failed, In September of 2006 Honda produced a  Campaign for a P0420 where is ECM PGM - FI was updated for a lean running condition that deteriated the catalytic convertor rapidly, This Campaign from Honda is a indefinitely warranty. for the ECM upgrade.but not for the catalytic convertor. TSB # 05-028