why p0430 with a new cat?

Question

I replaced the (defective) factory catalytic integrated manifold with a header and Magnaflow free flow catalytic converter.
Unless I drive really lead footed, the computer kicks out the P0420/0430 code.

What can I do to fix this? why does a brand new catalytic converter throw this code?

Answer 1

The code for the catalytic convertor may just be a false code. The downstream 02 sensor which are the catalytic monitor sensor may not even be working properly. . The best way to resolve this is to use a scan tool with a data stream and see that the front 02 sensor are switching properly. and that the rear 02 sensor stays above .650 volts. Also these catalytic convertor are known sometimes to fail when there is a cold air intake kit installed, the reason is the vacuum to the fuel pressure regulator is displaced. adding the proper vacuum line to manifold  resolve the issue this is if you have a cold air intake kit