Audi A6 The mid-sized Audi A6 model offers more room to the driver and passengers over the A4 line.

CEL: Code P0421

  #61  
Old 10-26-2011, 08:53 PM
1st Gear
Join Date: May 2011
Posts: 14
Default

Originally Posted by MetalMASK View Post
Not sure if this will work but it certainly is worth a try. Yes you guessed it, my audi just had the very same problem (code P0421) and I came across this thread from google search.

The dealer quote me 1500 in replacing the Passenger side catalytic converter, I checked online and it seems that aftermarket is much cheaper (around $300)but according to dealer, aftermarket may not make the CEL go away...

From cheapest to most expensive....I am gonna try
1. Techron
2. Get a cable and follow testing procedures to see if it really is CAT problem.
3. replace CAT.....

btw, my audi is also 3.0, 2004 A6 3.0 Quattro.

Thanks to all who posted in this thread. I will report back my experience.
You're on the right track, I ended up selling my car. I had some funky code come up regarding the transmission. I say no way!!! I'm a student and don't have the time or money to deal with problems on a bi-monthly basis. Prius's are my new best friends.

Btw, seems like the A6' 3.0 problems are easier to deal with. The A4 3.0's are basically as you discover them, as in, the cat light comes on, then the cats need to be changed etc. I changed the coils, spark plugs, coolant temp sensor (which apparently can trigger rich fuel mixture and cause the cats to go bad) and ran a full tank with the AUDI recommended fuel system cleaner... still didn't go away, so I went and got Techron fuel system cleaner from Chevron and still experienced the same problems.

I would definitely have a professional check to make sure the O2 sensors are still good.

Get a Prius and with all the money you'll be saving on gas you can buy yourself a super car for the weekends

Igor
 
  #62  
Old 10-26-2011, 08:57 PM
1st Gear
Join Date: May 2011
Posts: 14
Default

Originally Posted by MetalMASK View Post
Not sure if this will work but it certainly is worth a try. Yes you guessed it, my audi just had the very same problem (code P0421) and I came across this thread from google search.

The dealer quote me 1500 in replacing the Passenger side catalytic converter, I checked online and it seems that aftermarket is much cheaper (around $300)but according to dealer, aftermarket may not make the CEL go away...

From cheapest to most expensive....I am gonna try
1. Techron
2. Get a cable and follow testing procedures to see if it really is CAT problem.
3. replace CAT.....

btw, my audi is also 3.0, 2004 A6 3.0 Quattro.

Thanks to all who posted in this thread. I will report back my experience.
Also, if need be, when replacing the cats, make sure that they are checked out and that someone you know or someone on the forums has already used them as a replacement parts. A lot of after market cats get put on and will be ok for like 3k then fail again!!! CHECK!!!!

Igor
 
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