levin818 is right.
When you do not connect the ISCV connector, it will allow a certain amount of air to flow into the engine for idling. For the 3 pins, the middle pin is connected to +12V, when you supply ground to the 'open' pin (on the side where the bottom of the connector has a notch), the valve will open more and allow more air in (less resistance). When you supply ground to close pin on the other end, the valve closes a bit and allow less air, but never totally block air. The ECU will alternate the ground to both these pins to control the idle.
When electrical load is high, high beam on etc, and with air cond compressor running, gear in D if auto, ECU will alternate higher duty cycle to the 'Open' pin to maintain idle.
If you test as how levin818 says and cannot hear clicking sound, clean it with petrol etc. If still cannot click give it a few gentle taps to free it. Sometimes it is stuck. If you measure with multimeter between middle pin and either end pin if open circuit it means the coil is damaged and you need to replace the ISCV.
I'm using the ISCV to control idle on 4G15 with silvertop 4 throttle and it works great. This is a good ISCV.