GM Genuine Parts Nitrogen Oxide (NOx) Sensors are designed, engineered, and tested to rigorous standards, and are backed by General Motors. The information from these sensors is used by the engine control module (ECM) to adjust various parameters to help reduce harmful emissions. GM Genuine Parts are the true OE parts installed during the production of or validated by General Motors for GM vehicles. Some GM Genuine Parts may have formerly appeared as ACDelco GM Original Equipment (OE).