audi a4 b8 o2 sensor signal p2196

Hi All, My engine emissions light came on for my Audi A4 2.0 Tdi. I got this checked out at local garage and mechanic plugged in the VAD machine which spitted out this erro O2 Sebsor Signal P2196 Rich Bank1 Sensor 1 Too Rich. The mechanic reset the alert and notified me it was a fuel issue...