Plenty of info if you do a search of the archives.
P0430 is bank 2 pre-cat efficiency below threshold. Simply put, the signals of the pre-cat and post-cat sensors are compared in order to imply proper catalyst operation. If the cat is really bad, the manifold/precat is covered under the 8/80 emissions control warranty. A way to verify is to swap the bank 1 and bank 2 post-cat sensors. If the code changes to a P0420 (bank 1 precat) then you know the sensor is bad. If it stays as a P0430 you need to get it replaced.
AL
