Oxygen, Lambda Sensor Exhaust Oxygen Sensor (O2 Sensor) Measures oxygen in the exhaust so the ECU can correct the air-fuel mixture Mobiletron "OS-B559" - Not availableBMW - 3 (E46, WB), X3, X5, Z4; MERCEDES-BENZ - C-Class, E-Class; AUDI - A3, TT