Brian_LA

New to the forums. Have an 03 A4 Q 3.0L manual. Just got the CEL P0431. I know it's the drivers side bank cat problem. What I want to know is the following:

Are there any CA legal cat replacements (I live in Los Angeles)?

IF there are no decently priced CA replacements (I have not found any replacement system that are legal in CA) can I buy a non CA legal system and put it on my A4 and still pass smog?

Additionally, what do the CA legal systems have that the non-CA legal systems do not have?

and the long shot questions:

Are there any fuel additives that can clean the carbon from the cat without damaging fuel systems or fouling plugs?

Can you modify non-CA legal system to become CA legal?

Thank you in advance for the information and advice.

Brian_LA

Is this forum just dead?

clancy

I have zero knowledge about CA requirements. But, I find it odd to believe if you bought the Audi part from an Audi dealer it would be offered in your state if it was illegal. That said, there are many times Audi fault codes indicate a CAT problem that is not really a CAT problem. Many people have discussed this over the years on this forum and/or on the C5 forum. I would spend some time doing searches on this site. You will likely find the resolution.

It is not a dead forum, but it is pretty quiet due to the age of these B4 cars. Most of the DIY have bought newer cars. Mostly all that remain are the people who recently bought one really cheap and now find out why. But, again, spend time searching the archives. I am confident your answer is there.

In Colorado where I live, I was able to solve my 2.7 engine CAT fault codes by replacing O2 sensors and installing a spacer on the rear most O2 sensors. I do not know if this would be acceptable in your state.

Brian_LA

The part from the dealer is $1,300. Obviously the part from the dealer is CA legal. Its the third party aftermarket parts that are non-CA legal. Most non CA legal cats cost 1/4 of what the new part from Audi costs.

I'm trying to learn if there is an integral difference between CA legal and non CA legal cats and if i can just use a non CA cat.

I did a lot of research and most of what I found with the P0431 code is that you can waste time and money replacing sensors, but the overwhelming consensus, here, and on other websites was simply to replace the cat.

clancy