On-Board Electronic Controller and On-Board Device Control Method

To apply an on-board electronic controller having a relay control driver circuit for performing ON/OFF control of a relay that connects and shuts off a wire from a battery. The on-board electronic controller includes: a switch circuit that is connected to an output unit of the relay control driver circuit to draw out a current; and a control circuit that activates the switch circuit when an abnormality occurs in the vehicle, to cause the switch circuit to draw out the current from the output unit so as not to turn on the relay. This prevents sticking of the relay to ON even in a case where an output harness of a relay control driver is short-circuited to another signal harness or a power supply and GND line.