Suicune doesn't have access to Snarl. It was switched with Hidden Power before it was released.
If you have enough fast TMs, you could flip Extrasensory once to see what type Hidden Power your Suicune has, then flip it back if you don't like the type. (Don't bother wasting more fast TMs trying to get a different type. The Hidden Power type is locked in for each individual pokemon.)
