Question

2005 Nissan Frontier V6, the Service Engine Soon light is ON and I got the P0420 code

Answer 1

most likely the Catalytic converter needs to be replaced. If you use low octane gas you might want to think twice after you get it replaced it is very expensive so if you want to replace it use 91 octane gas it will save the catalytic converter in the long run

Answer 2

P0420 NISSAN - Catalyst System Efficiency Below Threshold Bank 1
Read more: https://www.autocodes.com/p0420_nissan.html