Correction: It's code P0421, not P0241. Sorry for that, it won't let me edit the thread title.


I have a 2003 audi a6, with 53k miles on it. My check engine light came on last night. Took it to Advance Auto Parts and this it the code that came up. The guy said that it is either an oxygen sensor or the catalytic converter.

I had my catalytic converter replaced 5 years and 1 week ago at the Audi dealership (the 1 week might be significant), and only 13k miles ago. I don't drive many miles.

So is it more likely the oxygen sensor? Or do you think I will need to replace the catalytic converter again?

As far the cat that I got 5 years, am I probably screwed with regards to any sort of warranty, if that is indeed the problem? I know there are federal warranties and such, but I am literally 1 week past 5 years, so I am not sure if anything would be covered.

I will add that the car hasn't been driving well the past year or so. I have had a hunch something wasn't right based upon the way it has been driving. Similar symptoms that may appear when oxygen sensors weren't acting right. I had a full tune-up, had an exhaust cam sensor and MAF sensors replaced (prior check engine issues), but it still didn't get better. So maybe the sensor finally just failed? The car is 9 years old and the sensor have never been replaced.

Would appreciate any insight! Thanks.

 

The CEL is on when the efficiency goes beyond 96%, that is it is on when it is 95%. If there's nothing wrong with the cat, you can get CEL off by adding spacer on the O2 sensor after the cat, or one like this

Plus you can drop a bottle of THIS in your full tank of gas.