Oxygen, Lambda Sensor Exhaust Oxygen Sensor (O2 Sensor) Measures oxygen in the exhaust so the ECU can correct the air-fuel mixture FAE "77439" - Not availableAUDI - A4, A6, A3, A5, A8; VW - Golf, Caddy; SEAT - Ibiza, Altea; SKODA - Fabia, Octavia