Essentially, stepper motors are digital actuators; in other words, they are either on or off. They move in fixed increments in both directions, and can have over 120 steps of motion.
Stepper motors are commonly used to enable the ECU to control idle speed. In most fuel injection systems, the stepper motor controls an idle air bypass built into the throttle body.
In an idle speed control valve (ISCV), (located in the air intake chamber) a stepper motor is built into the ISCV where it rotates a valve shaft either in or out. This in turn increases or decreases the clearance between the valve and the valve seat, thereby regulating the amount of air allowed to pass through. The ISCV stepper motor allows 125 possible valve opening positions.
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