Bosch LSU 4.9 Wideband Sensor by Haltech A wideband oxygen sensor (commonly referred to as a wideband O2 sensor) is a sensor that measures the ratio of oxygen to fuel vapor in the exhaust exiting an engine Features Suits Nexus ECU Suits Elite Pro Plugin ECU and WB1/WB2 Benefits Measures the ratio of oxygen to fuel vapor in the exhaust exiting an engine Applications Universal What’s In The Box? 1 – Bosch LSU 4.9 sensor 1 – Factory calibration resistor connector Warranty This sensor is strictly non-refundable if this packaging has been opened or tampered with.