[ddvk]

cltmmm:

Diagnosing the root cause of P0420/P0430 is almost the most difficult thing in the ODB2 codes. Manufactures map all emmision issues like O2/pre-cats/cats onto these 2 codes.

Hoping you are doing some basic maintaince like plugs, air-filters, fuel-filter and basic tuneups to injectors... Lets start to understand ur issue...

1) Have you ever replaced your O2s? If you haven't I would start there...
2) Have you ever smog checked your vehicle? If not needed in your state, then run a basic exhaust test with AAA and check the numbers vs averages. You will be surprised the pre-cats/cats work just fine..

BTW, cats/pre-cats usually are designed for the life of the car (I didn't say that, that is what the manufacturer says), but I would be surprised you fouled the cats/pre-cats with poor gas and maintainence...

Finally it boils down the maintaince, poor maintainence on plugs, filters, tuneups will foul the O2 sensors and eventually the pre-cats/cats...

I would start replacing the O2 sensors, if you haven't already done that along with plugs and filters. Good luck you have your hands full with these 2 codes.!!!