Oxygen, Lambda Sensor Exhaust Oxygen Sensor (O2 Sensor) Measures oxygen in the exhaust so the ECU can correct the air-fuel mixture StartVOLT "VS-OS 2004" - Not availableCITROËN - Xsara, C5, C3, Saxo, C2; PEUGEOT - 206, 306; MINI - Cooper, Clubman