P0420 is commonly caused by exhaust leak, intake leaks, injector, spark plugs or incorrect timing. So there are some things to check out before CAT replacement. This code is not indicative of contamination as your engine. The CAT is the 3-way on Bank 1.
P0507 indicates a faulty PCV valve onlt in combo with P0506 is releaen needed.
Also Nissan has recall on CATs damaged by oil from engine of the 2.5L
Monday, May 18th, 2009 AT 11:30 AM