Don't write this off as a repost. I haven't been able to find clear cut answers anywhere.

Car: 2000 A6 2.8 (C5)

Ok so, I got 2 codes out of my computer today. P0431 and P0421. They're catalyst codes apparently.

Now on to my questions.

1: Is there a possibility that these codes don't mean a have bad cats?

2: Is there any way to adjust my threshold with vag-com?

3: I know the 3.0's always have bad cats but does that apply to the 2.8's?

4: Do the non foulers work on C5 2.8's? Or would I need a "Waynes
Block" from Vortex?

5: What would happen if I gutted my cat? Engine life wise? Performance
wise?

I've looked for conclusive answers to these questions but have only scratched together enough to come up with some guesses about what I should do. If I don't have to buy cats I won't. I'm a biker so pardon my willingness to gut the cats. They're gutted on both my bikes, lol.

 

1. I could be the ECU software issue. Ask a dealer to check your software version, and update it, if not the latest. When they did mine, they charged about $300.
2. No.
3. Catalytic coverters in 2.8 also do go. As you probably know, they are not cheap. So check the ECU software first, then the oxygen sensors the the coverters.
4 and 5. It depends on your state's emission regulation.

 

Thx for the answers. State regs aren't a problem, since I can buy my inspection here. I'm just worried about the car itself.

 

Your car will run better with gutted cats.

 

Would You have to do something with the sensor behind the cat? that is the one that tells the ECM the cat is not working.

eagle research makes a EFIE to adjust the voltage to O2 sensors, That way the sensor will be sending the correct range to the ECM and won't trip a CEL anymore. They are primarily used for the front two sensors. The ones used to adjust Air fuel ratio.

Maybe it would be fine if you just take it out and cable tie it to the frame. Just wondering about that wasn't going to try it myself or anything

 

I noticed gains on my bike but only after remapping. How these cars run on stock maps with gutted cats??

But do you think the cats could actually be bad???? I'd do one of the O2 bypasses (Waynes Block or Non Fouler) and leave the cats on if I knew they were good.

The car shows no signs of being slugish, they're no stalling, or odor. How else can I tell the condition of the cats? She has 200k mile BTW.

 

With VAGCOM you need to check measuring blocks 34, 35, & 36. And for the catalytic converter tests, you need 46 and 47. Basically start with the measuring block 34. Your car should be at normal operating temperature, start the car, step on the brake and keep the RPM somewhere between 1400 and 2000. Test will turn itself on once the car thinks it is ready. Repeat 35 & 36, and do 46 and 47.

34 - Bank 1 before Cat O2 sensor aging test
35 - Bank 2 before Cat O2 sensor aging test
36 - Bank 1 and 2 after Cat O2 sensors readiness
46 - Bank 1 Cat converter conversion test
47 - Bank 2 Cat converter conversion test

FYI, 46 and 47 will initialize only after completing 34 and 35. At the end of each test it will tell you whether the component is ok or not ok.

 

Awsome, I'll run this as soon as my cable comes in the mail.