i have a macbook A1989 that has taken water, i cleaned pcb with ultrasound and i noticed this missing component. It is not present from the brd scheme I have available, how do I identify it?
can someone help me?

Q8401-SI7812DN

This is not Q8401
There are no elements in this position.
This is a damaged conductive track.
You can just put a jumper.
But this track itself could not be damaged. Either there is a short circuit after it, or it is specially damaged by someone.

I was referring to the small component at the top of the capacitors, in the diagram it is not shown but on the pcb it was present

pls

Indeed, there is an element.
But let's think logically.
The bus on which this element is installed PPVOUT_S0_LCDBKLT.
This is the display backlight bus.
Where can this bus go? In fact, only on the J8500 connector, for 43 pins.
Check if you have a connection from the PPVOUT_S0_LCDBKLT line to pins 43.
Most likely there is no connection. And according to the scheme, there is a connection. This means that this element has a safety function.
This can be a zero resistor, fuse, or inductance.
I think any 50-60V fuse with a power of about 1W (55V * 0.015A = 0.825W) will do.
Can be replaced with a jumper for testing. But be sure to check that there was no short circuit on the side of the J8500 connector (this could cause this element to fail)

It's so easy

thanks ;-), I will follow your suggestion, I am learning and I am a beginner

R 0.8 Ohm