Oxygen, Lambda Sensor Exhaust Oxygen Sensor (O2 Sensor) Measures oxygen in the exhaust so the ECU can correct the air-fuel mixture ACI-AVESA "SLS-13321" - Not availableCITROËN - ZX, Xsara, AX, C5, Xantia; PEUGEOT - 405, 406; FIAT - Ducato, Ulysse