my friend has a 01 civic and it had a check engine light code was p0420 catalyst system efficiency below threshold bank 1 so i changed both o2 sensors and code was still there and plus a p1457 emission control system leak detected (control canister system) came after i changed both sensors. any clue? i dont think it is the cat i would think thats unlikely. any help would be good thanks

 

P0420 = bad cat

p1457 - have you checked the gas cap seal?

 

really how can a cat go bad you dont really need it

 

Your cat eventually does go bad. It absorbs poisonous fumes and pollution. Eventually it cannot absorb any more and thus is not doing its job.

You do need it. it kills the air, contributes to greenhouse gasses, and (from what I understand) if you are caught without one you can receive a ticket for it - regardless if your state/province has sniffer tests or not.

Besides, between a proper high-flow cat and an ebay test-pipe... you gain a whole whopping 1hp. not worth it in my books

 

You don't need the cat but your ECU does, otherwise it's going to turn the CEL on.

 

dam so thats the cat thats the headers correct?

 

so some one correct me if im wrong but thats the header cat?

 

I'm not sure on the 2001 models, but I know that the 96-00 (I own a 97) the exhaust manifold and cat are one piece from factory. A non-honda branded replacement is 2 piece... exhaust manifold is one piece, and the cat is separate. They just bolt together and fit like a factory stock piece.

If you plan on doing the work yourself its not that difficult, esp if you have an oxy/acetylene touch handy. (I used one to slightly warm the nuts holding the old manifold on. I was scared of snapping a stud off)

Also, disconnect the battery and remove both O2 sensors before you start (make sure you know which one is upstream and which is downstream)

And once you're done putting it all back together, fire it up and let it idle for a good 10 minutes. This lets the computer re-learn what its like to have a full-working cat again