A nitrogen oxide (NOx) sensor is an emission control device that measures the amount of NOx in the exhaust system of a diesel engine. It is a critical component of the Selective Catalytic Reduction (SCR) system, which reduces harmful emissions by converting NOx into harmless nitrogen and water vapour. The Cummins® 4326864 4326864RX 5WK96750C NOx sensor is designed specifically for use in Cummins® diesel engines.