Need CA Cat

First replace the O2 sensors. Will have to anyways and more times than not, new sensors will "fix" the problem. Use antiseize on the threads.

How many O2 sensors are there?

Two? Or more?

Non-turbo 2 cat Subaru system.

Thanks!

Before you go spending a lot of money on parts, spend a little time checking things out...

I found a clogged vacuum line after 2 O2 sensors...

OK, I think more info will help...

Based on what I have read, it looks like the front O2 sensor is fine, the rear/post cat O2 sensor could be slowing down.

The "before" O2 sensor slowing would trigger another code, the after one might not.

I can see the before, I will have to go hunting for the after...

Thanks for the info so far!

Question: Is any welding required to replace the cats? It looks like I might be able to do this myself with a little ingenuity. I know the nuts will not be easy, but I would probably choose to crack them off anyways.

Cats are usually bolted in, but on Toyotas they may be welded. If it is a welded system (usually the welded system is from the cat back to the muffler) you can cut the welds, flare the front pipe or adapt a new pipe, AFTER placing the clamps on the pipe, of course! and get a universal cat that will fit.

Most Toyotas (Oh, SNAP! Wrong group!!!) er, Subarus have a y pipe that comes into the cat and then the rest of the system attaches to that.

Subarus usually have 2 cats, a forward and an aft. Here in Mass we have what's called 'California emissions', meaning the environuts got a hold of the legislature and adopted the CA standards. I have an '89 GL Coupe and when we put the exhaust on we 'skipped' the rear cat. The car passed emissions with almost new-car readings on one cat! However, if they put the car oon the lift and you only have one cat you're going to have to add it back.

Good luck!