2002 B5 S4 45xxx
After Market Diverter Valves

I need help figuring out what this is before I take it in, if I do...

My engine light came on and recieved the following fault code when scanned. I had hust had a temperary APR Chip Upgrade Installed. For all who dont know, its basically a trial version good for 6 hours so you can love the result and spend the $600 to buy the permanent one.

Fault code 17585 "Bank 2 lamda correction downstream of Catalyst; control limit attained"

I had the code cleared and the temp chip has expired. The check engine light has not come back and it has been 2 days.

Can anyone help me figure this out please? Maybe bad cat? or o2 sensor?

 

See if you can get enough slack to swap the Bank 1 and Bank 2 secondary O2 sensors. Clear codes. See if the code follows the sensor, or if it now shows up under Bank 1.

If it shows up under Bank 1, it's the Cat. Otherwise, it's the O2.