Oxygen, Lambda Sensor Exhaust Oxygen Sensor (O2 Sensor) Measures oxygen in the exhaust so the ECU can correct the air-fuel mixture LEMARK "LLB935" - Not availableCITROËN - C5, C4, DS3, DS4, DS5; PEUGEOT - 308, 508; DS - DS 3, DS 5; SAAB - 9-3