Apparently the diagnostic codes only cover electrical box faults not mechanical problems.
To self test put ignition on ( do not start engine), over drive on ( light is out),connect TE1 and E1 terminals together on the diagnostics port ( to right and under steering column)
Normal should give 2 flashes on 2 flashes off on the overdrive light.
If not let me know the code displayed.
If no code shows do the manual shifting test by disconnecting the shift solenoid loom at the rear of the gearbox (Ignition off) and drive the car starting in L shift to 2 then 3.
If the car changes up/down thru the gears manually this is probably good news from a mechanical point of view.
Let me know what happens.
Cheers,
Steve