Hello, i needed to replace the same (rear) catalytic converter of my 2006 Honda Pilot LX (2WD) in less than 16 months. The first time it happened in October 2014 when the vehicle had 160K miles (Car’s service code was P0420), and the second time it happened this month (same code P0420), when the vehicle had 184K miles. I have it replaced at Honda Service (Lute Riley in Richardson, Texas) both times.
When it happened for a second time so quick (160k miles wth first converter vs 24K miles with the second converter), I asked Honda Service for a free warranty replacement, but they said it only has 12K miles, and 12 month warranty on repairs, they called Honda corporate to see if they would do anything extra (they did not), but Lute Riley gave a discount to do it at their part & labor cost only ($800 first time vs $550 second time).
What could be the cause of the second catalytic converter to go bad so quick? I have been the owner and only driver of the vehicle since i purchased it new and my driving habits have not changed.