The problem is, "XXX Fault - Repair needed" is a generic error message, you need to plug something in to even remotely have an idea on what's going on.
Not sure if gearbox problems issue a normal fault code. If they do you could perhaps get get a cheap OBD2 reader and use that.
Currently: 2017 Jaguar XE R-Sport 25t - Caesium Blue
Previously: 2011 CitroŽn DS4 DSport THP 200 - Babylon Red