So, it's been a couple weeks that my 2002 audi a6 3.0 quattro keep giving code 16805 16815 which is basically warm up catalyst efficiency below threshold for both bank 1 and 2. Normally i just clear the code and it will come back after couple hundred miles. It's getting annoying, so i do a test with vagcom to see whether the cat is really bad or not. I did the pre cat and post cat o2 sensor check and then i go to the cat converter aging test; surprisingly it passed every single test, even for block 002 and block 003 (maf test). I'm really confused on what's wrong with it. Any help will be appreciated. thx

 

If you have less than 80k miles, hurry up to the dealer for free cats...
Otherwise, replace the pre-cat sensors and go from there.

Is your exhaust smelling like rotten eggs? If not, you may look also into checking the ECU for a firmware upgrade.

 

unfortunately the mileages is 88K, so yeah no more federal emission warranty. However, i really doubt that the sensor and the cat are bad, because it passed the vag com test and muffler shop test pretty damn good. Any other idea beside the ECU reflash?

 

Winter gas. I have the exact same problem starting two weeks ago. Since it doesn't affect driveability, it can stay on for a while.

 

Audi ECU software threshold may be too sensitive or narrow ranged. The CAT is not bad, just a little off the ECU spec. & the CEL came on all the time.

One of Audi TSB was issued here : http://www.vaglinks.com/Docs/Audi/C5...0Reference.pdf

Unfortunately your car does not fall in this TSB and dealer won't give flashing even you want to pay for it. They'll tell you that your car doesn't have an update for flashing.

If you don't have bad CAT symptoms: no emission problem, no sulphur smell, no rattling CAT, no significant bad performance.
plus FREE replacement of CAT is not in your book and the CEL is annoying, you may check on this Min-Cat-Cel-Fix link www.bigdaddiesgarage.com

I think a lot of good CAT were changed and throw away b/c of these P0421, P0431. Another suspected is BOTH are not supposed to go bad AT THE SAME TIME, usually won't be such a coincidence.

 

I have the same problem, will the car pass inspection with the CEL lit?

 

sabjarb-depends where you are i know most places in the north east will fail you right away if the CEL is on

 

If you didn't change your sparkplugs for long ... change it then run a bottle of CRC guranteed to pass (G2P) and see if the CEL will go away. It used to call the 'CAT Cleaner' ... in Amazon I saw some good words re this ... it is about 12.00 no big deal even it does not work... find it in Advanced Auto website.

Make sure dealer changes your coilpacks for FREE under recall.

 

Bigdadi,
Thanks for the G2P advice, you made a believer out of me. Passed inspection with flying colors.

 

Nice to see another believer ... I put a bottle in my tank even i don't have CEL. Inspection this week so time to repalce my headlight (burn-out).