HO2S21 harness is open or shorted
HO2S21 circuit poor electrical connection
Engine Light ON (or Service Engine Soon Warning Light)
HO2S21 System Too Lean is the generic description for the P1147 Audi code, but the manufacturer may have a different description for your model and year vehicle. Currently, we have no further information
about the P1147 Audi OBDII code.