Given the very low production numbers of the Insight its unlikely and aftermarket CAT company will offer replacement CATs. However, I believe that some will reman a core you send. Expect several days down time. And from my expereince don't expect such a CAT to last much longer than the warranty provided.
Yah, the cost is usually much lower, but that's because not as much of the good stuff is put in there (gold and palladium (another rare earth metal comperable in price to gold) etc). So the _actual_ cost per mile may not yield any savings. You'll have to do the math based on cost and decide for yourself.
A P0420 occurs when the secondary O2 sensor essentially "wakes-up" and begins to give readings similar to the primary sensor. This means that the CAT is no longer "scrubbing" the exhaust and a code is set. Yes, a restricted CAT may also code but as Dan pointed out its NOT the primary complaint.
And its an unusual mode of failure in most makes and models.
You should verify that this was the actual failure on removal (visibly clogged) AND determine the cause. Commonly its a misfire condition causing a CAT overheat and a subsequent melt down. Else your replacement CAT _will_ suffer the same fate. $$$$
But anything causing incomplete combustion will also take its toll e.g. a bad _primary_ O2 sensor.
It's been quite a few years since I've done any quality reading on OBDII, their associated monitors and responses. It may be that when a P0420 is detected OBDII requires a reduction in power to help reduce emissions AND otherwise "protect" super heating CAT (they'll glow bright red) and a possible consequental FIRE
Laws governing what type of replacement is required vary from state to state and possibly locality (EPA non attainment zones). Any local repair shop should know or where to find out before beginning the job.
HTH!
Alternative or high performance catalytic converter?
