This is what's up. I'm workin with a 98 civic DX hatch..... I had a cracked header so I replaced it with a Megan header and went with a Magnaflow catback exhaust. Now I get the CEL and ODBII throws a P0420. What's the deal? My 02 sensors are less than a month old. Anyone have any suggestions to get this worked out?

Also, is there a way that I can get my car to pass CA emissions while still keeping my header?

Thanks for any help.

 

A code P0420 may mean that one or more of the following has happened:

Leaded fuel was used where unleaded was called for
An oxygen sensor is not reading (functioning) properly
The engine coolant temperature sensor is not working properly
Damaged exhaust manifold / catalytic converter / exhaust pipe
Retarded spark timing

We can probably eliminate the leaded fuel (I hope), and since you just replaced everything, it's probably not the "damaged" one. Did you have to rewire either of your sensors? Do you have any exhaust leaks? Did you maybe damage the sensor when you were handling it? Getting some dirt in it/on it or even the grease from your fingers will mess it up. The cat may be going bad.

You will not pass smog unless you header is CARB approved, and trust me, they will notice an aftermarket header. Anyway, they will definitely not pass it with a CEL.

 

Thanks for the help and quick reply! I'll check it out.