In a method and apparatus for fail-safe controlling an electronically-controlled
throttle-type
internal combustion engine, provision is made of two accelerator position sensors and two
throttle position sensors. When either one of the two accelerator position sensors or either one of the two
throttle position sensors fails to operate, a low-speed fail-
safe operation of a minimum compensation, that is, an operation for maintaining a minimum output required for limp-
home control operation of the engine, is executed and, then, a first fail-safe control operation is executed for controlling the position of the throttle valve using a value detected by the remaining sensor. Therefore, the throttle valve is not unintentionally opened, and the operation can be smoothly shifted to the first fail-safe control operation. When the operation for decelerating the engine is detected by a sensor of a
system separate from the above-mentioned sensors, the first fail-safe control operation is interrupted and, instead, a second fail-safe control operation is executed for holding the throttle valve at a predetermined position in order to assure the low-speed fail-
safe operation of the minimum compensation.