DangerDad

My 2001 A6 4.2L has developed these engine codes on a recent trip and I had to get my car towed:
If indeed one of my catalytic converters is failing, is my only option to buy new from a dealer? I called Shokan Used Audi parts and they said it is illegal to sell a used catalytic converter? I had no idea..hence my ignorance on this subject.

However, if all other parts and sensors are working correctly, will a failing catalytic converter alone prevent my A6 from running properly? My car has 150K miles, so the idea of buying a new cat is not that appealing.

I don't want to break the laws for emissions, but Indiana does not require annaul emission tests on cars. Just looking for cheaper alternatives, if there are any.

SloopJohnB@mac.com

It wouldn't be the first time someone took a used cat off a wrecked car and installed it. But Shokan is correct, it's illegal for THEM to resell a used cat.

I'd fixe the evap emission control flow problem first, then check the 02 sensor(s). The efficiency below threshold is dependent on 02 sensor readings. 02 sensors are a LOT cheaper than cats and often replacing them increases fuel mileage as well.

Who knows, you may also have a bad fuel batch situation as well.

VONBOTTLE

if the o2 sensors don't fix it and you have to replace the cat, just get VAST's piggie pipes ($460 + core charge for the 4.2) - that solved (knock on wood) my efficiency below threshold code i had for a couple years. there is a reflash from the dealer that's supposed to fix that issue on certain model years - yours may fall into that category, you'll have to ask the dealer. i have an '00 2.7 and the reflash did not fix my CEL - it did for a few days, but it came back. i've had the piggies for a few weeks now and so far no issues.

massboykie

Could be. I had this happen twice after using Shell Sonoca. with different tanks inbetween.

I am chipped though so it might be more sensitive, but try a new batch of fuel from another brand and see.

Also, although they cannot sell it to you, you can always use an aftermarket cat. You have to get them welded in though, but I bet the total will be nothing compared to getting them from the dealer. A freand got quoted almost $2k for his 2.8 Passat ( i think labour was in there too). I have to believe ours will be similar if not more.

I would second Piggies though, might as well gain some power whiel you are at it... ;-)

Cheers
Massboykie

Old Salt 64

I am pretty new but am also getting a cat code on my 03 A6 3.0 and did locate OEM cats on auto anything in the 300-400 range and universal as low as 108. Don't know about form, fit, and function until I pick the car up and look.

ajg617

Just curious, are you also getting the evap code on your 03 and did your 03 have the roll-over valve recall? My 03 A6 Avant is getting both the CAT (except it's bank 1) and EVAP codes that you are getting on your 01 but I'm kind of thinking that I have an EVAP issue because the CEL started coming on after the roll-over valve recall work that was done by the dealer. Every time I run the car to fill up with fuel, the inside of the gas cap is soaked with gas which makes me think there is a pressure build up inside the tank. I'm just wondering if the cause of the CEL for the CAT is actually a matter of the EVAP threshold being less sensitive or taking more time than the O2 readings and so the CAT code throws first but isn't the real issue.

Old Salt 64

I don't have any history on the car. Codes I am getting are for the bank 2 cat efficiency below treshold, Bank 2 CMP (Exhaust) and codes for leak down on cam adjusters. Was advised maybe better fuel and injector cleaner would clear the cat code and I will change the cam position sensor but probably off to the shop for cam adjuster gaskets.