My car is a 2000 A6 quattro 2.7T with 116,000 miles.

When I boughtthe carjust overyear ago the seller told me it had a bad catalytic converter (as diagnosed by our local Audi dealer). The car passed emissions and I wasn't having any problems so I left it alone. Now I keep getting the P0421 code,it's making somenoise and my gas mileage is starting to slip,so I guess I'm ready to replace it.

I don't want to switch to Piggies or any performanceexhaust - I just want to put in a good catalytic converterthat has the bung for the 02 sensor and call it a day.

Two questions:

1. Any recommendations for just the catalytic converter? Again, I want something that's either OEM or exact of original but I don't want to spend a million dollars.

2. Is the cat on this car weld-in or bolt-in? I have access to a lift but no welding equipment so if it's bolts I'll do it myself, otherwise I'll have to get a muffler shop to do it.

Thanks for your help.

 

1. If the car passes emmisions the cat isn't really bad, the O2 sensors are very sensitive and there is a TSB for re-flashing the ECM to correct this. If the flash has already been done and its still throwing a code then you should replace the cat. The factory cat for a 2.7T is $600.

2. The cats are bolt in, and kind of a PITA to get out.

 

Thanks for such a quick reply, auditech79.

I asked my local dealer about the TSB for reflashing the ECM and they said that based on my VIN my car didn't qualify. (???) Does that sound like misinformation?

They also told me that the 02 sensor on that bank was replaced on that side just before I bought the car. Since I'm getting some noise and decreased fuel economy, is it a good bet that the cat is bad?

Or should I pay the $250 to have the dealer reflash the ECM before I spend money (and time) on the cat?

 

if you just need replacement cats get magnaflows, they are after market but cost only 50, a shop should be able to weld them in for maybe 50 more.

 

Good luck on having a shop weld in new precats, you have to do it out of the car. All the ECM is looking at is the precat. 2.7 cats have the second o2 right before the main cat.

 

2002 1.8t quattro. Local garage changed cat with an aftermarket type - from "Emico" it was supposed to work. After driving for 15 min 'engine light' came on. Went back to garage the next day. "Catalytic converter efficiency" was the code on the cpu, no other fault codes were present so... Garage ordered another aftermarket unit (we thought the 1st unit was defective), this time from "Bosel". After driving 15 min to Hamilton, the 'engine light' came back on again. Went back to garage - some head scratching later, the cat downstream sensor was changed, but that did not solve the problem. Now, both aftermaket units were recommended replacements (on a stack of bibles)by the suppliers.
The next step is to get an Audi dealer supplied unit.....before doing this however, is there anyone that has had a similar problem? There are no misfire codes, faulty injectors etc..... because there are no fault codes relating to any other fault except the "cat efficiency" one. Can it be, that the only unit that will do the job has to bought from an Audi dealer? Can Audi stoop so low? Don't answer that.