Here is something about the newest BMW software ISTA+ v4.01.22 Voltage Control, just pictures. Simulates voltage of connected interface (all interfaces).
only recommend for diagnostics.
It is version specific, in standalone version for ISTA 4.01.22 from:
This is to satisfy the voltage requirements in ISTA when programming over ENET interface which does not report voltage. Also it will not be a permanent mod. Closing down the tool will revert ISTA back to real time voltage monitoring (on the fly).
If just car idling causes overvoltage, you really need to check the voltage using multimeter ASAP. If its really that high, fix the alternator or its regulator. If not, then you may have faulty ICOM, but overvoltage is really bad for the car.