Dave,as all were satisfied with your diagnose and solution -also, I must say - Thanks a lot!
I got the same DTC with Skoda Octavia II 1.9l TDI BXE engine with the DSG AT - and I replaced the all things that were involed - like Engine ECU,Vacuum Box included,(N75 N18 & N345),vacuume lines,Turbocharger with the all EX manifold - and after every road test I got it again - it's start well,drove in first gear,second gear VSS - about 80Kmh and no more gear changes - but when I leaved the gas pedal it's change the gear to D3 but the ECU was in this time in limp on...
I searched around the world for such an experience - but nobody put it's finger and said
more than I wrote - when I read your experience and with your Ford Scan tool - I saw the last line...and for me it was the Fixed - as we all are saying...I replaced the Mechatronic and done the road test about 3-5 times and - no more P0234!!!(the gears were change correctly and in time...).
Always I said as FORD/MAZDA sub dealer(in the past) - the WDS and the new scan tools - were very friendly in such DTC's - more lines with possible causes!!!
Thanks again - Dave