PURPOSE: To attaine safe operation of a vahicle, by obtaining predetermined accelerator conditions by switching the control mode of an electronic governor to all-speed type by means of an electronic control unit, and thereby enabling to back up operation of the vehicle in case that error is caused in an accelerator sensor system.

CONSTITUTION: Output signals of a sensor 1 producing an engine-speed signal, a sensor 2 producing a signal representing the injection quantity of fuel, an actuator 3 for actuating a governor, a sensor 4 producing a signal representing an injection timing signal and a sensor 5 producing an accelerator signal are furnished to an electronic control unit 6. The electronic control unit 6 applies driving signals to the governor actuator, a timer solenoid valve, etc., and the electronic governor controls the injection quantity of fuel by picking up signals from the above sensors 1, 4 and 5. In case that trouble is caused with an accelerator sensor system 5, the trouble is backed up by switching the control mode of the electronic governor from limit-speed control to all-speed control and thereby obtaining predetermined accelerator conditions.