Oxygen, Lambda Sensor Exhaust Oxygen Sensor (O2 Sensor) Measures oxygen in the exhaust so the ECU can correct the air-fuel mixture LEMARK "LLB544" - Not availableAUDI - A4, A3, A6, A5, TT; BMW - 3, 5; VW - Golf Plus, Touareg; ALFA ROMEO - 156, 159