Oxygen, Lambda Sensor Exhaust Oxygen Sensor (O2 Sensor) Measures oxygen in the exhaust so the ECU can correct the air-fuel mixture Mobiletron "OS-B509" - Not availableBMW - X5, 3, 5, 1, 6, X3, 7, Z4, X1; AUDI - A4, A3, TT, A6, S6, A5, A8, R8