Oxygen, Lambda Sensor Exhaust Oxygen Sensor (O2 Sensor) Measures oxygen in the exhaust so the ECU can correct the air-fuel mixture LUCAS "LEB554" - Not availableBMW - 3, 5 (E39, WB), Z3, 7, X5; AUDI - A6, A4; MERCEDES-BENZ - E-Class, C-Class