dynamoose

Hello everyone, I'm new to the forums and Just recently purchased a 2000 A6Q 2.7T 6MT, I bought it fairly cheap and it needed ALOT of work (Still does) in my quest to eliminate the many DTC this vehicle has I've managed to get the extensive list down to 2 codes.
P0441 (Evap purge incorrect flow)
P1606 (ECU rough road spec ABS) [vehicle has a bad ABS control module]
I ordered a used but tested OEM Purge valve solenoid from a local German used auto parts vendor and installed it. My old solenoid wouldn't click at all and after installing the replacement solenoid you could clearly tell it was operating and click. I cleared the codes and all was good.
My drive to work the next morning the light came on. I figured yeah the p1606 will still come up but that should be the only code. However after reading the codes I now have 3 codes. P0421 (Warm up catalyst efficiency below threshold bank 2) and P0431 (Catalyst efficiency below threshold Bank 1) as well as the P1606. These codes we're never present before replacing the purge solenoid. is it now that the purge valve is operating it has realized the cats are bad? or does this indicate another issue? Perhaps even though it clicks the replacement solenoid is faulty? Any insight would be greatly appreciated. I'm trying to do right by this car, I feel like I need to save the vehicle as it was so neglected in it's past life and deserves the maintenance to bring the vehicle to its factory glory.
I'm new to german cars as far as owning But i'm no stranger to difficult repairs as I also own a 1994 3000gt Twin turbo which IMHO is fairly more difficult to work on ;P

tester123

Evap purge DTC could be due to few things:

That N80 or evap purge valve
Bad gas cap (seal around the gas cap most likely).
Potential leak when pressurizing the tank.

Thanks to strict emissions, the operation is as follows:
After starting, gas tank is pressurized with a pump and monitored if the pressure drops. At this point, if the solenoid is stuck open or a leak in the gas cap, or a leak elsewhere in the fuel system would cause the pressure to drop and set the DTC.

The other cat issues could be due to bad oxygen sensors.

Clear the codes, set readiness as per manual and see if they come up again.

dynamoose

Thanks for the reply. To be clear I no longer have an Evap code present. Only P0421,P0431 and P1606 after I replaced the purge valve. The P0441 is gone and was just wondering if it was a coincidence that the new catalyst codes came up after the purge valve was replaced. The vehicle has 182K miles on it so I can't rule anything out.

dynamoose

I also forgot to mention that in the extensive CEL list it did have quite a few codes for B2S1 and B2S2 oxygen sensors. Both of which I have replaced. And the respective codes no longer exist.

tester123

Clear them one more time and see if they come back again after setting readiness.

Also, see TSB 26-08-07 (TPI 2013086). -Technical Service Bulletin- there may be a firmware update if your engine is ATQ.

dynamoose

I'm assuming I'll need VCDS and the cable to do so? I haven't invested in one yet I have only an ELM Bluetooth reader to pull codes.

tester123

can you clear codes? Readiness can be set automatically after driviing 50 or so miles ..I forget exact number.. Or, it can be done following the procedure in service manual.

Not sure about the capabilities of the adapter you have. Visit Ross-tech.com and compare.