It worked occasionally, but most of the time didn't produce any sound. Often it would be fine when I turned the car on, but then after a few minutes of driving it would cut out and then wouldn't come back.
The guys at the dealership checked all the connections and signal sources and all seemed fine, so I guess by process of elimination they've decided the sub is stuffed. Hopefully it gets fixed, it's a bit of a pain having a problem so early on but I guess I'm fortunate that it isn't anything major/mechanical.

