4-wire Lambda (oxygen) sensor, suitable for CFMOTO 520 and 625 models (part number 018B-176000). Tested and approved by the 3,000+ member "Off-Road Knights" community, this product is essential for keeping your off-road vehicle's engine running efficiently and economically. The Lambda sensor measures the amount of oxygen in the exhaust gases and sends data to the engine management computer, which adjusts the fuel-air mixture accordingly. Quick and easy installation in place of the original sensor.