Epiphenomenalism and functionalism are conceptually independent -- at least, there is no obvious relation between them such that one would imply the other. I've also never heard functionalism as the claim that "consciousness is not epiphenomenal", despite having heard at least 25 different authors use the term.

A standard formulation, from the Stanford Encyclopedia of Philosophy, is:

Functionalism is the doctrine that what makes something a thought, desire, pain (or any other type of mental state) depends not on its internal constitution, but solely on its function, or the role it plays, in the cognitive system of which it is a part. More precisely, functionalist theories take the identity of a mental state to be determined by its causal relations to sensory stimulations, other mental states, and behavior.

Your usage of epiphenomenal is also too imprecise. It means not that some system has some extra quality, but that there are two systems operating in parallel or in something analogous to a parallel manner, such that there is a base phenomenon that causes the epiphenomenon but that is never in turn influenced by the epiphenomenon.

A good example of an epiphenomenon would be Plato's Allegory of the Cave: the people on the walkway, and the light, are the causes (i.e., base phenomenon) of the parallel system of shadows on the wall (i.e., epiphenomenon) that the prisoners see and take as real agents, but the shadow system has no influence at all on the underlying real system of the people on the walkway (assume they are unaware and have never actually seen the shadows behind them).