JustinChase

I got the following codes with the VAG-com

4 Faults Found:

16804 - Catalyst System; Bank 1: Efficiency Below Threshold - P0420

16814 - Catalyst System; Bank 2: Efficiency Below Threshold - P0430

17831 - Secondary Air Injection System; Bank 1: Insufficient Flow - P1423

17819 - Secondary Air Injection System; Bank 2: Insufficient Flow - P1411

Readiness codes only failed the O2 sensor section (forget the exact name)
last time I cleared the codes it had 3 readiness failures, cats being one, and I can't remember the third.

the CIL has been on for years, but occasionally goes off, and I run to get my test immediately. It hasn't gone off for almost 2 years now, and I'm way past due for a new sticker. When it first went on, the dealer said I need new cats, I said don't need to give them $3k

Car is 2001 A6 Avant 2.8L V6 with 167k miles

Car's in fine shape, but worth maybe $2500 to anyone else but me.

runs fine, MPG is lower than I'd like, computer says about 17mpg

I only care to fix it because I need to pass the emissions test.

how to resolve, as cheap as possible?

can I just reset the codes in order to pass the test and be done, or do i really need to throw money at it?

I'm just using the shareware version of the vag-com software, and have no problem paying to register if it helps, but I've read and researched for hours, and I don't know that a registered version helps me any.

I don't really want to buy the full version with their cable for $250 JUST for this problem, but will do that it I KNOW it will fix it so I can pass the test.

any other solutions?

if replacing the cats with aftermarket is necessary, can i just get the cats and have them welded in, or should I get the entire exhaust, which one?

I really don't want to get rid of the car, but I'm not going to spend more than it's current value just to pass the stupid test.

thanks in advance for any help.

4Driver4

Call Audi and see if your car is eligible for an ECU reflash. Fix the secondary air problem. Check 02's.

4.2Crew

Secondary Air System is likely a vacuum issue and easy to check. Check the entire vacuum system... From the intake manifold to the combo valves and everything in between. Easiest done with a hand-held vacuum pump (Mity-Vac?) with a vacuum gauage attached and outputs test with Vag-com. Once the vacuum system checks out, then ensure secondary air pump is blow'n well.

devinsixtyseven

There are a few great posts on checking functionality of the combi valves, and checking/fixing the SAI pump (on the cheap, even).

Maybe your cats are fine, maybe they are foul, and maybe it's the oxygen sensors. When did you last change the sensors?

There is a very good chance your mileage readings are directly the result of the cat/oxygen sensor issue. Learn to check and fix these things yourself, there is no reason as you say to give the dealership 3K$ to fix this.

JustinChase

Thanks all. I'll look for the posts about the combi valves and SAI pump.

I was thinking that since I don't have a vacuum pump would it just be easier to replace all vacuum lines as opposed to trying to figure out if there is a problem with them someplace? I read in another post on here that someone said they may look fine, but get cracks with time, and 10 years and 167k miles would qualify.

I've not looked into any of this work yet, since I was thinking only about cats and O2 sensors prior to these great replies/suggestions.

the O2 sensors were replaced at about 110k, maybe 120k, I can't remember, but they didn't resolve the CEL for very long after they were replaced, which confirmed in my mind that it was the cats, but maybe not, or maybe it's those and these new things.

Am I correct in assuming that the codes indicate the downstream O2 sensors, vs. the upstream ones?

Can I also assume that that would make them easier to get to and replace or is that just wishful thinking?

4Driver4

The codes indicate that the delta in the reading that the ECU sees between the front and rear O2's is not high enough.

Call Audi with your VIN. Ask about the reflash.

JustinChase

Audi USA says there is no outstanding campaign or recall for this, but to call my dealership.

I remember the dealership telling me there was a possibility that flashing the ECU* might resolve my CEL when it first happened, but that they wanted $150 to do it, and they didn't think it very likely to fix the problem, just a chance.

*I think it was reflash the ECU they said, it was a few years ago

Anyway, I'm calling them now.

Dealership guy said he didn't know anything about reflashing an ECU, but to bring it in and they'd know more after they put in on their computer.

I told him I knew all the codes, and provided them to him, and he said he'd call me back. I don't believe he will.

any other ideas or suggestions?

JustinChase

he did call back, and said he asked around and no one knew about reflashing the ECU, but if I paid him $125, they'd put it on their computer then they'd know if a reflash would work.

he couldn't explain how they don't know about a reflash, but their computer will tell them if a reflash would work. nor could he explain how their computer would tell them anything I didn't already tell them. he talked in circles. useless.

they are the only Audi dealership in town, and clearly don't deserve 125 of my hard earned dollars

any ideas?

thanks again.

devinsixtyseven

I encountered this attitude with one shop for certain, and suspected it with another...the idea that you owning an expensive car means you should give them the car, and an expense account, and then get the hell out so they can write up an invoice. As Mel Brooks so succinctly put it, "we have to protect our phoney-baloney jobs here, gentlemen!"

Are there any good independent Audi shops in your area?

Read the first couple pages of this, before you do anything else. Yes, different car and slightly different engine configuration, but SAI is for the same purpose on your car:
http://www.vaglinks.com/Docs/Audi/TT...TT_Sec_Air.pdf

First thing I would do is correct the SAI problem. Fixing the pump (something I need to do myself, and why I remembered that PDF) might only cost you 12$ and some time.

I suspect there's a very good chance that what seems like a cat/O2 sensor issue may be a byproduct of a faulty SAI system. SAI is much less expensive to fix, you know it's screwed up, and it's upstream...what say the more experienced minds?

BTW, a quick search at Ross Tech says the same thing for the SAI codes...

http://wiki.ross-tech.com/wiki/index...9/P1411/005137

JustinChase

I've gone to 3 so far, and none seem particularly good, and aren't really any cheaper than the dealership, and have all told me I need to replace the cats, so I have to say "no" so far.

I'm in Austin, TX, so you'd think there'd have to be someone.

I'll read that PDF, and $12 to eliminate a potential issue is certainly on the short list. Thanks for that.

as an aside: I DO want to fix this, but is there any way to force all the readiness codes long enough to get my stupid sticker, so I can continue the troubleshooting without that hanging over my head?

The only one that failed was the O2 one I mentioned, and the testing place confirmed one being not ready would not fail me (but no more than one), so if I can reset then force all the rest, I could pass, but how to do that??