<p>A processor of an electronic control unit performs at least one of a first diagnosis process of determining whether or not a switching element is abnormal based on a signal output from an abnormality diagnosis circuit in a state where a first diagnosis voltage supply circuit is controlled to supply a first diagnosis voltage to a control line and a second diagnosis process of determining whether or not a pilot signal line is abnormal based on the signal output from the abnormality diagnosis circuit obtained in a state where a second diagnosis voltage supply circuit is controlled to supply a second diagnosis voltage to the pilot signal line.</p>
