Oxygen, Lambda Sensor Exhaust Oxygen Sensor (O2 Sensor) Measures oxygen in the exhaust so the ECU can correct the air-fuel mixture LUCAS "LEB4004" - Not availableBMW - 3, 1, 5 (E39, WB), 6, X5; MERCEDES-BENZ - E-Class, C-Class; PEUGEOT - 308, 207