Oxygen, Lambda Sensor Exhaust Oxygen Sensor (O2 Sensor) Measures oxygen in the exhaust so the ECU can correct the air-fuel mixture NTK "1896" - Not availableCITROËN - C4, Berlingo, Xsara, C5, C3; OPEL - Vectra C, Signum; VAUXHALL - Vectra, Signum