P0155 AUDI HO2S21 Sensor Heater Circuit
Possible causes – Faulty Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1– Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1 circuit fuse– Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1 harness is open shorted to ground– Heated Oxygen Sensor (H2OS)