Oxygen, Lambda Sensor Exhaust Oxygen Sensor (O2 Sensor) Measures oxygen in the exhaust so the ECU can correct the air-fuel mixture Delphi "ES21244-12B1" - Not availableCITROËN - C4, C3, C2, C5, Xsara; PEUGEOT - 307, 206; FIAT - Ducato, Ulysse