820-01521 Air board with no keyboard

[sekidata]

I have this 2018 Air board that is fully functional except for the keyboard. It initially had liquid damage on the trackpad, which I replaced. Now the trackpad works but the board only responds to the keyboard during pre-POST period (startup key combinations), nothing thereafter.

I already tried a known good keyboard & flex cable, DFU Revive, and NVRAM reset. External keyboard works fine, too. Apple Diagnostics passes with no issues found.

Any advice as to where to start testing?

 

[2informaticos]

That means KB only works in USB mode, before macOS is loaded.
Then should work in SPI mode and doesn't.
TP works in both modes?

Try another TP board and flex too.

 

[sekidata]

Every known-good topcase I test this board in ends up with a shorted trackpad which prevent the keyboard from working. I already had to replace 3 trackpads killed by this problem board. I will need to delegate this logic board to the donor pile… it is pure evil!