Oxygen, Lambda Sensor Exhaust Oxygen Sensor (O2 Sensor) Measures oxygen in the exhaust so the ECU can correct the air-fuel mixture VEGAZ "ULS-651" - Not availableAUDI - A8, Q7, A4, A6, A3; VW - Jetta, Golf Plus; BMW - 3, 5; CITROËN - C5, Xsara