You could also try to shift it from 1 - 2 and see if it shifts fine.
The Manual 1 and 2 will override the Solenoids.
If it holds each gear, at least you know that the hydraulics and mechanics are working,
and that the problem is only electronic.
If it still drops the gear while in 1 or 2 then it could be that your tranny is due for a complete rebuild.
