Engine code

[backayrdauto]

I have a 99 civic DX. The problem i am having is there is a code coming up that states P0420 (catalyst system effeciency below threshold). What does this mean? The catalytic converter, a leak, and which sensor should i start with checking? I greatly appreciate your time in this matter!!

[240slider]

you need a cat .If the vehicle is under 80k It still maybe covered under warranty