OK, so I need to replace a cat and am not sure which one I need. From what I can tell from being under the vehicle, there are 2 cats off of each exhaust manifold with oxygen sensors after them, then there's another cat or resonator further down the line without a sensor after it. I need the cat that's on the back bank. I don't want to pay the $500+ Lexus or an auto parts store wants. Just wondering what my options are on this and if I can go through somewhere like RockAuto to get one, part numbers, etc. All help is greatly appreciated. Thanks.

 

Did they tell you what the error codes you were getting? You can go to most any parts store such as AutoZone or Advance Auto Parts and they will attach a scanner to retrieve any codes being thrown. If you let us know which ones you are getting we can better tell you what is going on and perhaps give you specific advice.

In the meantime you can have a look at the following. While not exactly the same there is enough for you to work with.

https://www.clublexus.com/forums/rx-...30-2004-a.html