I did a search in the RX 330/350 forum and didn't seem to find any patterns.

I had to have one of the cats replaced today. It was covered under the 8/80K warranty on the cats. However, this is the second cat to be replaced on this car. The car has 65,000 miles. I think that there are 3 cats on the RX. I'm just wondering if there was a problem with the cats on the RX or if I'm just having a weird issue for some reason. Thanks for reading and any input.

 

What code was it throwing? Was it O2 sensor related? Two Cats sounds like something else is the root cause and the Cat is just the failure point.

 

It was the P0420...cat insufficiency bank 1...this time. I'm not sure which bank it was the first time.

 

That's related to the catalytic converter underneath the vehicle, there are 2 more with 1 off of each engine bank. If you open up the hood and look off the front engine block you will see one of these cats, known as precats.

You might have gotten some bad gas somewhere and it could have caused an issue with the cat.

Another possibility I am aware of is that if the cat were even partially clogged for some odd reason and then you go through some water, enough heat combined with water and you get a ruined cat. However, since this was your second cat, it most likely was an issue with gas somewhere. I saw this code repeatedly on other vehicles when I lived in Mexico and I used to think it was just the vehicle was not tuned right, but when I started seeing even new vehicles having this code pop up I knew the gas was largely to blame.

 

Thanks for the information. I'm hoping that is was just some bad gas. It would seem so as I can't find others on here that have had this issue.