code po 420 Cat efficiency
 

I have an 03 civic 1.7 code po 420 cat efficiency?? Help

This code generally means that the catalytic converter is toast. Any other CEL codes? Is the engine misfiring?

Thanks Ron
 

Yes it had an intermitant missfire which was caused by the cam position sensor which I have replaced! Since then the Engine has run great! just keeps setting the 420 code occaisionally

Unfortunately, the misfire problem that you have now fixed permanently damaged the cat.