Provided is a control system that can appropriately determine whether or not supply of power to a load is abnormal, and can specify a detailed reason of the abnormality. A control circuit supplies power to a load and shuts off the supply of power in accordance with a power supply/shutoff instruction to supply or shut off power from a battery to the load. The power supply/shutoff instruction is output from a microcomputer to the control circuit. A control unit determines whether or not the supply of power from the battery to the load is abnormal, based on (i) whether the power supply/shutoff instruction output from the output unit is to supply power or shut off the supply of power, (ii) the value of a current flowing from the battery to the load, and (iii) the value of a voltage applied to the load, and specifies a reason of the abnormality.