Electronic throttle control system and method

An electronic throttle control system performs open-loop control on a motor (5) of an electronic throttle (1) by pulse width modulation (PWM) control based on a target opening amount TAR set by an accelerator sensor (8). A microcomputer (11) controls the current output to the motor (5) by periodically controlling an excitation width of an on-pulse with a specified duty ratio. The microcomputer (11) calculates a duty ratio corresponding to the set target opening amount TAR with an accuracy higher than its own resolution. When the calculated duty ratio exceeds a value of the output resolution, the microcomputer (11) adds, e.g., every other cycle, a value having the output resolution to the duty ratio of the on-pulse which is periodically controlled, and averages the current output to the motor (5).