My drivers side mirror is not adjusting on my 00MY. It can move from side to side but not up and down. The passenger side adjusts correctly. Where do I start to look for the problem? Does the mirror need to be replaced or could it be a loose connection?

Sounds like a dead motor - had that on my old 306. On that it was a whole new wing mirror, not sure with the Impreza, if you do need a new one try one of the salvage places like Grade A Subaru......