rally

Unfortunately, no.

MP4.2+6.0

While I don't recognize the issue personally, this reply makes sense to me. Per my earlier question, it was recently tuned up so that is eliminated. Running rich is rare; lean is the norm and most commonly a variety of vacuum leaks, or sometimes fuel starvation. Also the two sensors in tandem reporting pre and post cat with essentially opposite conclusions suggest to me this is probably not a sensor failure, but something in the fuel system itself. Many true sensor issues also have specific electrical codes that basically tell you it is physical wiring or a burned out sensor heating element. None of that is the case here--not seen in the codes. Pre cat (B2S1) reading is rich, while post cat it is lean, which tells me so far the cat is working hard and scrubbing the exhaust (for now...). The codes are also both bank 2, meaning the same side of motor--U.S./continental Europe driver's side. Suggests issue is thus on that side. Since car has a high pressure fuel pump (HPFP) on each side/bank, another possible confirming clue. Then within fuel you would be down logically to injector leakage or other issues or an HPFP issue. If it were an injector (or HPFP) running lean, you might have ignition misfire codes too, but for rich those are unlikely.

As a practical matter, an HPFP costs on the order of $400 parts wise--not sure about dealer price but a quick indy parts check got me to that #, which resonates true with a VW HPFP I bought. Easy typically to change out--very accessible on top of valve cover area. If dealer pokes at it very long, in the real world diagnostic labor bill will add up to the parts cost before even getting to the fix. Can't be definitive on this--especially arm chair--but one of those where practicality may say reasonable answer/educated guess is to change it out.

yaya

Update: the dealer did end up replacing the HPFP on the driver side got the car back drove it maybe 100 miles and the code is back. Dropping it off tomorrow morning

Steelcover

Have a 2012 S5 with very similar issues, P2098 and P2198. Replaced O2 which lasted 200 miles before the error returned. Was wondering if yaya ever found a fix?

Steelcover

Troubleshooting update: Too clarify previous post, 200 miles ago (aprox a month ago) I replaced Bank 2, Pre Cat O2 to clear the Too Rich error P2198.
Last night 2/11/20 I swapped both, pre and post Cat, O2's from left to right. I want to see if the error follows the O2 sensors or remains on the drivers side. While making the change I did notice the Pre Bank2 sensor plug was not fully seated, "locked in place". After moving it to the passenger side, Still had the issue of not completing locking down. So I secured the connectors with a tie wrap. Fingers crossed the unseated connector was the reason for the P2198 P2098 returning, (unseated meaning-still connected just not fully pushed together and locked). Reset code and will report if the error returns.

Steelcover

Update: One month later and the error has not returned (sound of knocking on wood). Hopefully the issue was the connector.