Oxygen, Lambda Sensor Exhaust Oxygen Sensor (O2 Sensor) Measures oxygen in the exhaust so the ECU can correct the air-fuel mixture NTK "0051" - Not availableAUDI - A4, A5, A3, A6, S6; VW - Passat, Caddy; SEAT - Ibiza, Leon; SKODA - Fabia, Octavia