Ok, I get what you're saying, but wouldn't a bad O2 sensor that is causing me to get bad MPG throw a code for that sensor also? I mean, the Audi's are like sensitive girls; they cry about anything (gas cap)...

Also I am going in to audi Thursday for the coil pack recall, idk if they'll change'em cuz they don't look original, but hey it's worth a try. At the same time I am going to see if I can get them to check the firmware version and see if I need an update. I'll be starting a process of elimination sometime after that. Probably update if needed, spark plugs and air filter. And if none of that works, sensors ... if that doesn't work I'm rolling the car off a cliff then changing the cats.

 

Just had mine changed by the audi dealer - cyl 5 not firing properly (well not firing at all really). Can anyone tell me what the recall notice is?

I paid to have the chip replaced (controls one side of the engine). Performance we great for a few days - but now some minor missing.

And I have the 0421 - which came back on as performance slipped.
Coincidence?

I haven't yet checked the mileage - but will with the next fill-up.

 

The coil packs that came with the cars from the factory are bad, so it's like an IC (something to with lemon parts, I really don't know). So they're replacing them for everyone. I read about the recall online, shortly after I called my local Audi service department and asked them to run my VIN to see if I have ANY recalls. Don't be specific, they will only look up what you ask.

As for the P0421, I will try and ask them if they can check to see if the firmware in my car is up to date while it is in to get the CP's replaced, that way I won't have to pay them extra just to see if I have the current firmware.

Igor

 

That's exactly what I meant.

 

There is a trick remove this CEL if the cats are actually good, don't have the bad cat symptoms.

It is simply the Audi ECU is too sensitive and in narrow specs. Most time dealers are not willing to reflash the ECU to the most updated version if your VIN does not in their file of Audi TSB (even you pay for it).

www.bigdaddiesgarage.com

Before doing anything best call dealer first to see if the cats are still covered under Federal Emission Warranty (think 8 years, 80,000 miles) If it's then dealer will replace them FREE.
The cost is about $2800 for both cats replacement in dealer (stealer).

 

This MOD would be a last resort. The point here is to get your car to run the way it's supposed to. But hey I like that much more than using washers to displace the O2 sensors. Thanks for that. Going in to the stealer today at one to see what they have to offer.

Igor

 

ECU reflash may help but dealers are mostly not willing to do so ...

http://www.import-car.com/Article/79...and_p0431.aspx

 

If you receive any of these codes your first thing should be to check for any codes. Take care of any misfires or other problems. Second, go in to your data stream check your front o2 sensors. They should oscillate from 0.2 volts to 0.8 volts approximately. If they are not oscillating or if they show low or no voltage. You need to replace that sensor. Proceed to look at your rear o2 sensors. Rear o2 sensors should NOT oscillate and should typically stay flat from 0.2 volts to 0.45 volts. If they read zero, they are dead replace them. Now if your front o2 sensors are good and your rear o2 sensor is oscillating, that corresponding catalytic converter is most likely bad. Also any exhaust leaks can allow oxygen enter causing incorrect readings. One last thing, catalytic converters do not normally go bad. If your catalytic converter goes bad, look for a problem; misfires, coolant leaks, dripping injector, etc.

 

Quick note to share positive experience after reading several of the posts regarding CEL P0421: bought a bottle of Techron (NAPA $12.99), filled tank with Chevron premium. CEL disappeared in about 30 miles. This on my 2001 A6 with 122K miles. Had I only researched the site before paying to replace both CATS on my 1999 A4 just 2 months ago...Many thanks to those who shared info. Hoping for continued no-show for this particular error.

 

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.