Upon a predetermined first diagnosis execution condition being met, an electronic control unit executes a first diagnosis process of diagnosing whether an exhaust gas recirculation device has an abnormality based on an amount of change that a measured value of an intake air pressure undergoes as a result of a change in an EGR valve position. When a predetermined second diagnosis execution condition is met and, moreover, the first diagnosis process is not being executed, the electronic control unit executes a second diagnosis process of diagnosing whether an exhaust gas cleaning filter has a fracture based on measured values of an incoming gas temperature and an outgoing gas temperature.