As long as you dont have the SLABS ECU connected the road speed fault code should be logged in the engine ECU and it should trigger a CAN code in the autobox ECU too so if you have no code it means that the scanner you used is unreliable or something really odd is happening.... here's the table with CAN data exchange and if one of the elements from the list is missing that should trigger a fault code in this case the road speed(3'rd from bottom) which is that VSS described earlyer can't be there cos it's delivered by the SLABS ECU.... IMO for such project you better sell the D2 autobox and buy a D1 box instead cos that doesnt need electronic management...that's just an ideea cos i dont know how would that fit to a Td5Which ecu would the fault for the road speed show up as no faults show in engine or trans ecu