PURPOSE: To detect not only the abnormal condition of a fuel injection control system, but also the abnormal condition of the switching means of a relay for fail safe and the like.

CONSTITUTION: To a solenoid spill valve (SPV) 30 to regulate the fuel injection amount, a power source is fed through an SPV relay 86 of a constant closing type. The collector (output terminal) of the output transistor 87 of a driving circuit 84 to drive the SPV 30 is connected also to the input terminal of an abnormality detecting circuit 85. By connecting a pulldown resistance 95 between the input terminal of the abnormality detecting circuit 85 and a gland terminal, the output of the abnormality detecting circuit 85 is converted to the high level/ the low level according to the ON/OFF of the SPV relay 86, when the output transistor 87 is in the OFF condition. By deciding the output of the abnormality detecting circuit 85 by turning OFF the SPV relay 86 temporarily, in the engine stopping condition or in the OFF time of the output transistor 87, the OFF operation of the SPV relay 86 is checked beforehand.