The BCM (Body Control Module) is an electronic control module that monitors the electrical system. It also manages some functions such as tire pressure monitor, vehicle alarm, remote keyless entry, mirror heater, door locks, among others. The BCM also receives signals from the seat belt switch, ignition switch, cruise control switch, battery discharge protection, and other switches.
When the U0140 OBDII fault code is set, it is because the BCM is not receiving or sending a signal. This module has not been able to establish communication with the ECM via the CAN bus.