passenger door mirror not working. driver side does work. is there some kind of motor that needs to be replaced?

Have you tried pushing the button by the mirror switch to the right side? It can't be to the left or in the middle. If that doesn't work it should be under warranty if the Terrain has under 36,000 miles on it.

I have done what you said. Left works but not to right mirror. Terrain has 41,000 miles.

Well hen its the right mirror itself or the wires to it. Have it looked at by a reputable mechanic.

The switch at the door may be bad or a wire has come off. I believe the mirrors share the same fuse. If you have power to one mirror, start at the selector switch and go towards the mirror. Also make sure there are no obstructions preventing the mirror itself from moving. It wouldn't be a bad idea to check with the dealer and see if they either have had that problem before and know where to start looking, or they may say it is under warranty and fix it.