Common fault:- the gears strip internally and give your fault before failing totally.
found this article below which may help?
Since the ASV is an all or nothing unit (either open or closed), there is really no scenario where the unit should ever remain in a mid position.
You'll find four wires going to the device. Two for motor power and two to a position sensor. Spring tension will hold the valve normally open. Engine shutdown will apply voltage to activate the ASV motor, the valve shutter will cycle, and a flag will pass the sensor in order to signal to the ECU that the function has taken place... At least that's the way it should be.
If there is voltage to the motor and a ground path, you may expect the motor to cycle. If a high resistance path, then likely a partial cycle until such point as the motor is unable to overcome the homing spring.
Of course the sensor wires could also be a problem. If one or the other was crushed and partially shorted or open, then the ECU would receive spurious information and attempt to cycle the ASV based on false information.
My guess here is the ASV motor. Short of an obvious broken or shorted wire in the harness I expect the new unit will work as advertised.
