the vehicle fail to start.
(4) Trouble diagnosis: The electronic injection system will carry out trouble diagnosis for the
driving stage of the fuel injector. When the driving stage of the injector is short or overloaded to the
battery voltage, as well as short and open to the ground, the trouble mark level will be positioned.
At this moment, the closed loop control and the self-learning pre-control of the oxygen sensor will
be closed, while the self-learning data last time will be effective. The trouble mark level will be
repositioned after the trouble being removed.
9. Idle speed actuator stepper motor (Fig. 1-15)
Fig1-15
(1) Function: A by-pass air intake passage will be provided by the idle speed actuator with
stepper motor. When the throttle is closed, air will enter into the engine through this by-pass
passage. With a stepper motor, the ECU can adjust the size of the passage, and then confirm the
air volume into the engine. At the same time, the ECU can also adjust the fuel injection volume on
the basis of the air volume. With the stepper motor, the ECU can change the working condition for
the engine according to actual situations.
(2) Structure and principle: As a mini-size motor, the stepper motor consists of several steel
stators in a circle and one rotator. Every stator is winded with a coil. The rotator is a permanent
magnet, and at the center of the magnet, there is a nut. All the coils of the stators are connected
with the power supply constantly. As long as the current direction of one of the coils changes, the
rotator will turn for an angle. When the current direction of the coil of each stator changes in a
certain proper sequence, a rotary magnetic field will be formed, and the rotator of the permanent
magnet will rotate in a certain direction.
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