820-00840 no boot, but shows battery low symbol

Have an 00840 that has had no liquid damage, board looks like new. With the board out, nothing connected, it takes 20V at around .6Amps for the first 10 seconds, then shuts off.
In those 10 seconds or so, if I have it in the housing, It shows a battery-low symbol, sounds the charging-chime, and then shuts down.
All rails are present in those seconds, up to CPU vcore at .93v.
I have no clue where to look, does this sound like a BIOS issue?

**EDIT: This is a 820-00281-01, sorry got stuff mixed up
 
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God, i mixed up the boardnumber with another one here, sorry.
The actual board is a 820-00281-01.

Had to step away from this one for a couple of days.
I have now managed to get it to boot into an external Mojave installer after cleaning the ME region with Medusa2.
It will let me format the drive for a reinstall, but the reinstallation stops right at the mark where it;??s supposed to reboot and finish the install.
It does the same when it's running in SMC bypass mode.
I am a bit out of ideas on this one.
Also ran internet-based hardware test, but of course this found no errors..

*EDIT: it will not boot into an external OS. only the installer for some odd reason. I have tried both High Sierra and Mojave bootdrives.
 
I'm completely with you on cursing these machines..

I've tested with both J4401 and J4402 disconnected (those are for touch and display of touchbar right?),
seems to load faster, but now kernelpanics while loading High Sierra. (without leaving a fucking log, whats up with that)
In verbose boot it scrolls too fast on the big retina screen for me to read.
Tried booting into Mojave, there it just shuts down halfway.
 
had already cleaned ME region with Medusa2 earlier.
Or do you mean i should try a clean BIOS?
Do you have a dump i can use? cant find any on the web..
 
Hi 2info, thanks for the bios dump.
wrote it to the Mac, cleaned ME, same shit different day..

Hey duke, long time no see. If that's the case, i might try a RAM-reflow, or give up on it, spent too much time anyways.. what do you think?
 
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