In case anybody can use the info, I just powered up an E38 ECM standalone on the bench (nothing attached) and measured the 12VDC input current. The 12V B+ input (J1 pin 20) pulls about 140ma and the switched 12V inputs (J1 pins 19 and 47) together pull another 10ma. I'm using a 12VDC 1.25A plug-in power supply and it seems to be able to power this ECM standalone no problem.