ENGINE SYSTEM AND METHOD OF CONTROLLING THE ENGINE SYSTEM

In an engine system including an engine, and an exhaust gas recirculation device including a communicating pipe that communicates an exhaust pipe of the engine with an intake pipe, and a valve provided in the communicating pipe, and an electronic control unit, and its control method, the electronic control unit estimates the pressure in the intake pipe as an estimated intake pressure, and performs a jamming diagnosis to determine whether foreign matter is stuck in the valve, by comparing an intake pressure difference between a detected intake pressure and the estimated intake pressure with a threshold value, when a diagnosis condition including an opening change condition that the target opening becomes equal to or larger than a first predetermined opening and then becomes equal to or smaller than a second predetermined opening that is smaller than the first predetermined opening is satisfied.