Oxygen, Lambda Sensor Exhaust Oxygen Sensor (O2 Sensor) Measures oxygen in the exhaust so the ECU can correct the air-fuel mixture LEMARK "LLB112" - Not availableCITROËN - C4, Xsara, Evasion, Xantia, C5; PEUGEOT - 307, 406; FIAT - Ducato, Ulysse