autobox problems

[e30ata]

hi i am from the UK dont know if iv posted in the right coloumn but here goesgot a 325 with auto switchable box,originally the box was faulty so we thought ,sourced another then similar problem ,then decided to change the control unit still no joy,whats happening is that when you use 123 mode it seems to work fine as soon as you swith over to S or E mode the engine just over revs so these two modes(S & E) cant be used ,its been on the diagnostics machine in BMW and its not picking up the control unit ,but it did pick up the original unit ,had 3 technicians on this and there lost can anyone shed any light on this matter,thanks in advance