Your TCU is in Limp-home mode. There may be several causes, but the only cause I can think of off the top of my head is that one of the shift solenoids (1 or 2) is dead. Usually this is caused by a loose connection, but it can be caused by a short to ground also. There may be other reasons why the TCU would revert to limp-home mode, but this is the first one on the list.
Don't waste your time until you check for
trouble codes.