Oxygen, Lambda Sensor Exhaust Oxygen Sensor (O2 Sensor) Measures oxygen in the exhaust so the ECU can correct the air-fuel mixture Fispa "90430" - Not availableAUDI - A6, A4, Q7, S6, A3; VW - Lupo, Polo; PORSCHE - Cayenne; CITROËN - Xsara, C5