The K-Bus isn't connected to either earth or +12v it is a communication network transmitting data in a series of highs and lows.
If you have a part of the network pulled low, IE permanently earthed, then there can be no data transmission on any part of the network.
It is common, especially if the car has a sunroof, for the LSM to become wet, this can be seen quickly by removing the plug and inspecting the connector, in addition by unplugging the LSM and then seeing if the other items such as windows, central locking, ATC etc work, then either the LSM or the wiring to the LSM need investigation.
Brian
