Oxygen, Lambda Sensor Exhaust Oxygen Sensor (O2 Sensor) Measures oxygen in the exhaust so the ECU can correct the air-fuel mixture Mobiletron "OS-B4176P" - Not availableBMW - 5 (E39, WB), 1, 3, 6, 7; AUDI - A4, TT; ALFA ROMEO - 156, 166