and have code on P0420 P0420 - Catalyst System Efficiency Below Threshold (Bank 1). i had taken to ready honda dealership, they checked it gave me bill $ 110. and told me the because of poor gas, the light came on. but i alwys use 91 octane. should put in a new catalyst converter. plz reply thanks. light stays on,will go away for 15 minutes then come back on.

 

I always thought that you checked the secondary oxygen sensor first.

 

What model and year vehicle is this for?