The EGR valve (Exhaust Gas Recirculation) is responsible for controlling the exhaust gases through a regulation system of these gases that return to the cylinder. The PCM (Powertrain Control Module) decides the quantity based on conditions such as motor load, temperature and others. If the Power Train Control Module (PCM) determines that the quantity of exhaust gases entering the cylinder is not enough, the diagnostic code P0400 OBD2 is established.