•  The PCM energizes the closed-side circuit of the variable intake air shutter valve actuator when the engine speed is less than 4,100 rpm, closing the variable intake air shutter valve to enhance the inertia charging effect in the engine low to middle speeds ranges.

•  The PCM energizes the open-side circuit of the variable intake air shutter valve actuator when the engine speed is 4,100 rpm or more, opening the variable intake air shutter valve to enhance the inertia charging effect in the engine high speed range.