04 A4 Quattro, low miles, one owner, just got it, did Synth oil change, ran some fuel injector cleaner thru (car sat garage for a year) K&N drop in filter, having fun...suddenly, check Eng. Light. Run to Advanced where they read-erase it for free, readout says:" warm up catalyst efficiency below threshold bank one" Thinking this was kinda vague, had it read again, readout said " Possible O2 sensor defect, air entering ahead of catalytic converter Car drives fine, no probs, just hate the light....any ideas? Please, would like to have it squared away before I ship off again in 20 days. All tips ideas to: desertsnake1991@gmail.com. Thanks in advance

 

try to clear the fault code.

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Such a pain in the a** code to get rid up. You said it sat for a while? I'm wondering if the secondary air pump is running at cold start ups. If it sat and the moisture made it seize up, you would definitely get a warm up code since the cat would not be warming up as quickly as the computer would like to see. It's one of many possible cures

 

if u hear a loud whine from the front passenger side then your sai is gone. Trust me mines loves to scream on cold mornings. It goes away once the car warmps up. though i would say that it might be your 02 sensor or your cat taking a dump on you. bank one i believe is the 02 sensor closer to the front of the car.

 

Your going to need a cat. there is an 8 year 80,000 miles warranty for it depending on your delivery date / mileage

 

Agreed with Audi Tek. Warm up catalyist is a catalytic converter faulure code , nothing to do with the air injection running when cold.
There were some updates on some vehicles software but most of the time the cat will need to be replaced.
Use factory only , replace both o/2 sensors , no aftermarket junk.

 

The cat isn't always necessarily bad with those codes.

 

That's why is said Most! , not all!

 

I wasn't being a dick by the way haha. I see that you always give good advice, and yes I agree its possible its the cat. I have had this happen several times, sometimes its the cat, sometimes it isn't. Sort of ridiculous that its a shot in the dark dealing with this issue

 

Hey guys, I'm in Belgium n Germany in R&R, trying to get the real poopon this issue so I can tackle it he% on when I gt back to CONUS. Can't just be throwing parts at it...my experience is Cats work, or they get stopped up, simple as that. I had the code cleared at Advanced, came back 100 miles later. Like I said, car drives awesome, but the light bugs me big time. Help? Trying to avoid the dealership...it will morph into some kind of crazy 1500 dollar service bill, when AI probably just need an O2 sensor...