Remove the ICV from the engine, remove the hoses from it, clean it out with a carb or brake cleaner by squirting the product in each opening. Once it dries out, then squirt some WD40 inside of it to lube the internal plunger & spring.
To tell if it is functioning, after you have removed it from the car, get a multi-meter tester. Set the multi meter to OHMS. Test the ICV by using the leads of the multi-meter and touching the connector points on the bottom of the ICV. If the ICV is 100% good, according to online specs, you should see 20 ohms when testing it. If you see less than 20 OHMS, the ICV is not operating 100%.
Another way to tell if the ICV is turning "on" is to turn your key to ON (KOEO - key on engine off) and then feel the ICV valve (put your hand on it). If once feeling it you can feel a "buzzing" sensation, the ICV is currently on and is working (to what extent it's working would depend soley on the above OHM test). If you touch the ICV and you don't feel ANYTHING at all, the ICV is internally jammed and is not turning on... At this point is where you remove it and do the above clean & lube process.
After doing the clean & lube process, take a small hammer and tap the entire exterior casing of the ICV. Don't hit it extremely hard, but you want to hit it hard enough to jar the internals (spring & plunger) to de-jam it... Reinstall the ICV and start the car. If the car has a very high or very low idle, take your small hammer and tap the ICV again while the car is idling. If the idle changes (up or down) while tapping the ICV, then the ICV needs to be replaced, as the internal plunger is not functioning 100% as it should be...
You could try removing it and cleaning/lubing it again to see if it will function more smoothly - but depending on how old it is, how many miles are on it, how well the engine was previously maintained - sometimes the ICV will spring back to life, while in other instances, you will need to replace it...