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New member
2011 QX56 with 93,000 miles
Currently having an issue with both of my catalytic converters going out. Codes= P0420 and P0430. Also have a misfire, Code P0300. Per dealership, both cats (catalytic converters) must be replaced, no going around it. Cost is huge, about $4k plus. Was on the phone with Infiniti Consumer Affairs at 800-662-6200. There are no recalls for this and unfortunately for us we are outside of the Federal Emissions Warranty Law of 8 years or 80K miles to have them replaced for free. A case is being opened to see if Infiniti will cover the full cost. If they do not, I will be speaking with BBB to file a complaint and NTSA. I'll rattle as many cages as need be, this is absurd that before 100K miles both of my cats are no good and on top of this have a misfire reading that they are saying IS related to the sensors that are screwed into the cat converters. I'll do my best to keep this post updated.
There's a very long thread dedicated to this issue:

Infiniti Consumer Affairs won't be helping you, at least if it follows the pattern in the above post. You may want to call around some local muffler shops and see if they'll replace them doing the weld off/on technique, which will be a little under 1K.