All instrument seven segment LED displays not working

The instrument cluster, the climate control display and the fuel information center display are all "black" All the single led on the dashboard work. Anywhere there are seven segment LED displays they are "black"

Tried replacing Instrument Cluster and BCM. Checked fuses under the dash and under the hood. I haven't found any fuses in the trunk as some information indicates.

What makes me think it wasn't fuses is that when I would turn the ignition switch on I would get a very faded display on the speedometer (this is the digital speedometer, not the analog one), for a few seconds then scramble, then go "black". Which makes me think it is a voltage problem or a module loading down the voltages for all three displays. A fuse wouldn't act that way, but it doesn't mean it didn't blow a fuse along with the original problem. Then all seven segments went totally black and wont come on at all.

I replaced the BCM and the original problem indicated with the seven segment displays coming on barely then fading to black. Now once again I have nothing. I also tried unplugging the heater/AC control module under the BCM, in case it was bad and loading everything down but no change.

I am a 40+ year digital electronic tech but not an automotive one. I find the schematics less than adequate and scattered all over the place. It looks like the Climate Control module gets +5 and +12 volts. The instrument cluster schematic indicates a +5 volt input, and the fuel info center's schematic, I can't find.

I am going to check voltages tomorrow but I need to know the following:
Is +5 and +12 VDC the only voltages involved?
Is there another fuse panel feeding these voltages to the dash in the trunk somewhere?
Is there another module I don't know about which could be taking out all three displays?
Is the BCM and the ECM the same thing, and if not where is the ECM? I keep seeing this referred to both ways.

Thanks