Oxygen, Lambda Sensor Exhaust Oxygen Sensor (O2 Sensor) Measures oxygen in the exhaust so the ECU can correct the air-fuel mixture Denso "DOX-2030" - Not availableAUDI - A4, A6, TT, A3, A8; VW - Bora, Lupo; SEAT - Arosa; CITROËN - C5, Xsara