Oxygen, Lambda Sensor Exhaust Oxygen Sensor (O2 Sensor) Measures oxygen in the exhaust so the ECU can correct the air-fuel mixture RIDEX "3922L0345P" - Not availableSAAB - 9-5, 9000, 9-3, 900; BMW - 3, 5; AUDI - A4, A6; CITROËN - Xsara, ZX