i'd just remove the crome cover and make sure the valve is opening/closing properly,
as EC said you should see it turning one way then the other, if not disconnect the cables and try it by hand to make sure the valve turns, as it's more likely to be the servo that's US than the valve and a new servo is cheep cheep

if the valve is actually jammed, then that's when the problems start as the alen bolts that hold the valve in place will be corroded and a right bitch to get out and 9 time out of 10 you'll have to drill the buggers out