PURPOSE: To enhance accuracy in control for an air-fuel ratio and the like by obtaining a volumetric efficiency based on throttle opening and engine revolutions when functional disorders are indicated by an inlet air pressure detecting means, and thereby setting the controlled variable for the quantity of fuel injection and the like thereafter based on said volumetric efficiency.

CONSTITUTION: Inlet air pressure at the downstream of a throttle valve is detected by a means A, engine revolutions are detected by a means P, and the pressure dependent controlled variable of an object C to be controlled is set up by a means D based on the detected result of the detection. Thus, it is judged by a means E whether or not functional disorders are indicated by the means A. Throttle opening is detected by a means F, and the volumetric efficiency of an engine is concurrently set up by a means G based on the detected value of throttle opening and engine revolutions. The opening dependent controlled variable of the object to be controlled is set up by a means H based on the set volumetric efficiency. The object C to be controlled is therefore controlled by a means I based on the respective pressure dependent controlled variable and opening dependent controlled variable when the means A is normal and/or abnormal in function.