Oxygen, Lambda Sensor Exhaust Oxygen Sensor (O2 Sensor) Measures oxygen in the exhaust so the ECU can correct the air-fuel mixture APC "SAS970771" - Not availableBMW - 3 (E91, E92), 5 (E39, WB), 1 (E81, E87), 6, Z4, 7 (E65, E66, E67), X3, X5, X1