not a good sign...

http://forums.maxima.org/5th-generation-maxima-2000-2003/571342-got-p0430-code-not-sure-o2-sensor-bank-2-a.html

Seems when talking about P0430 on an infinity i30/maxima, most likly it means the cat is bad.

Couple of maxima onwers who got P0430 replaced their O2 (bank two, the reaar one) but NONE of them was able to clean the error code by doing that.

But as mada says, it is a cheap start of trying, a Denso O2 cost around $50 at www.rockauto.com
DENSO Part # 2344700

Replacing the CAT cost as much as $1300 (if you go to the dealer).

If you are not in CA, you may also order aftermarket one from www.rockauto.com, parts cost $120 -$400, installation will cost you $100-200.