M4NB00B5

I bought an A6 a while back and am now approaching my deadline for emissions testing. These are the 3 codes that are causing the MIL;

P0455
P0431
P0421

I've done my research on these codes and was hoping a simple fix could clear all 3. Gas cap is new and seals up fine. Already reset the MIL just to double check. I could not find any loose or split vacuum lines. Charcoal canister is not cracked or split either.

Any other suggestions? Where is the N80 valve located on the 3.0? Would a bad or defective N80 valve cause the 3 codes?

Thanks in advance

4Driver4

You'll get more responses if you post the meanings of the three codes.

M4NB00B5

As by request...

P0455 - Large EVAP leak
P0421 - Low Catalyst efficiency bank 1
P0431 - Low Catalyst efficiency bank 2

each of the codes had 4-5 reasons for what could be causing it

4Driver4

You probably need a new canister evap valve and two new cats.
Cat failures are common on the 3.0.

If your goal is simply to get through emissions, you may be able to fix just the evap leak then use VAG-COM to force readiness on everything but cat efficiency.

bigdadi

www.bigdaddiesgarage.com

Teutonix

Use O2 spacers to get rid of the cat codes for a quick fix. The codes is a result of overly-sensitive monitoring of the warm-up cats. Your car will almost certainly still pass emissions with flying colors as long as your main cats have not been tampered with. Search "O2 sensor non-fouler" or something similar. It's a $10 fix.

The EVAP leak is another animal. This one will take some diagnosis. I just went through this on my allroad, and found a damaged fitting on top of the tank that required removal of the rear subframe/suspension assembly, dropping the tank, and melting/remodeling the fitting to fix the leak. I should note that in my case, I frequently had a strong fuel smell near the gas filler area (particularly with a full tank). There are many other possibilities for this, so search the forum for "EVAP large leak" to get some diagnosis tips.

Philhawtin

I tried the big daddy's garage part and it did NOT work, which was a disappointment after believing it would with the "embedded honeycomb" since i had tried the o2 spacer from fast.

Neither worked for me..

JohnBoyToo

Will not fix mechanical issues, but I can vouch for this stuff:
http://rxpfuel.com/

helped my then friends car pass after it had failed the first time...


good luck...

2.7Lturbo

dont be a dick and fix your CATs properly, we all have to breath the same air

Philhawtin

You'll fund the repair then right!