Oxygen, Lambda Sensor Exhaust Oxygen Sensor (O2 Sensor) Measures oxygen in the exhaust so the ECU can correct the air-fuel mixture EFI "301178" - Not availableBMW - 5 (E39, WB), 6, 3, 1, 7; MERCEDES-BENZ - E-Class, C-Class; CITROËN - DS3, C4