Hi, I'll try to help you.
I've had a look at the wiring diagram for the SMG control module, pin 14 is '15WUP', essentially ignition on - wake up. I would expect this to be near battery voltage.
(diagram included with this message)
That wire seems to go back to connector X10547 somewhere behind the glove box, I've included another location diagram for you.
I would have a look at the connector, see if there is any damp or corrosion, I take it your car has the intelligent car access system, as it is this that supplies the power for the '15WUP' line.
If everything else is working fine then it is less likely that the issue is with the CAS module, as this supply would be for several systems.
Have you tried supplying battery voltage directly to the pin when the ignition is on with a piece of wire, through a fuse, to the battery to see if this is the actual issue?
Let me know how this goes.