PURPOSE: To enable accurate trouble judgement by detecting an accelerator manipulated variable, while calculating a variation in accelerator operation, and when this variation exceeds the specified value, having it so judged that something is wrong with an accelerator sensor.

CONSTITUTION: An ECI computer 11, performing fuel injection control over an engine E, inputs each output signal of respective sensors 12W17, 19, 22, 23, 26, 30 detecting an engine driving state, and it outputs a fuel injection control signal or the like to an injector 27. In this case, a variation in accelerator operation or a total variation per unit time in this accelerator operation is calculated from a signal of the value conformed to an accelerator manipulated variable to be outputted from an accelerator sensor 30 interlocking with an accelerator pedal 29. When this variation or the total variation exceeds the specified value, it is judged that something is wrong with the accelerator sensor 30, and the judgement is indicated.