I got my check engine light and checked it with the code reader and thats what it gave me.

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 or leaking exhaust manifold
/ catalytic converter / exhaust pipe
* Retarded spark timing
* The oxygen sensors in front and behind the converter are reporting too similar of readings

A code P0430 may mean that one or more of the following has happened:

* The catalytic converter is no longer functioning properly
* An oxygen sensor is not reading (functioning) properly
* There is an exhaust leak

http://www.obd-codes.com/p0420
http://www.obd-codes.com/p0430

Has anyone else had this? What's most likely the problem? I've realized a bad loss in performance/power. Also really bad gas mileage.

 

I would look for better info than what you find on that site. I had thought that 420 was a cam sensor code. Go to autozone or something and have them read your codes. It don't cost anything and the code description will be very specific, telling you that if it is an O2 sensor...it will tell you which one is giving the bad reading.

 

I did take it to autozone and thats what it said too. I didnt bother asking the guy there because he was a complete tool.