I go way back, before 1984, in computers.  IBM 360/20 in mid 60's.  VTAM/CICS, etc. NASA Telemetry processor programmer on the Apollo project. Flea power is referenced in more than Dell.  Its a DC voltage generated in a desktop power supply (when connected to AC Power.  Not in laptops and all in ones. My self built desktop has the flea power and indicator on the motherboard.
Hi ... a message longer than the title suddenly appeared on a full diagnostic screen when I powered my desktop. Options were Continue / Run Diagnostics / (something I don't remember). I ran simple diagnostics, got stuck in the middle. Ran comprehensive diagnostics, got stuck in the middle. Well, diagnostics were so secretive that they did not provide a single line of report. When run individually, both memory and disk tests got stuck, too. So I started to explore. Similar problem seems to be quite frequent in laptop versions; but they did not help, except for one: someone wrote something about a "flea" battery. The article is for laptops, but if you strip laptop specific actions, you are left with these steps:    1. Power off    2. Unplug the AC adapter    3. Unplug the DC power cable    4. Press and hold the power button for longer than 20 seconds to deplete flea battery    5. Plug the DC power cable    6. Plug the AC adapter    7. Power on Well, surprising as it was, it worked! Maybe it was just dust somewhere, I'm not sure. I suspect this flea battery the article talks about, is the battery providing clock ticks for the CPU. So, keep it in mind for troubling moments ...
Inspiron 5400 AIO (24) Power adapter not identified ...