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Not sure if DFU does an exhaustive check on the NANDs. The 20s cyling usually points to SSD problems. Some NAND may have bad locations.

Any history available? Did you check diode mode to ground on backlight output? J8500 gets 5V_S0SW_LCD?

Compare diode mode readings on big coils with good board. The drop on G3S voltages can be caused by a problem on Intel side power rails; S5 to S0.

You didn't say anything about 1V8 XA/B LDOs. What about PPBUS_G3H voltage and diode mode? Compare diode mode readings, between U3100/200, on all (4) LDO lines.

Many of the mentioned components connect with CPU; it may be damaged already. PMU_VDDHI is correct, so U8100 should deliver steady LDOs. Check them for voltage pulse and diode mode to ground. Also check U7700 LDOs. I suspect you have more corroded components, or traces; even under some BGA chips.

First of all, welcome to the forum! Is the CPU core steady 1.05V after 10-15s? PLT_RESET_L comes high? You should try known good BIOS. The data can be recovered with dedicated tool over Lifeboat connector (J9600), even if Intel side doesn't work.

U8100 generates more voltages from 3V8_AON. So 3V8_AON must be steady. Compare diode mode reading on it with good board.

Why don't you check left/right continuity, as above mentioned? I suppose that only few lines don't make good contacts.

https://openboarddata.org/?a=showboardsolutions&bpath=laptops/apple/820-01987

What customer said about problem appeared? Check diode mode to ground on the big coils; compare with good board.

May have another open line on the connector; check one by one.

Did you test the board alone on the desk? Which components have been affected by liquid?

"PP5V_S4_P2V7NAND_LB is 0V" There is a problem; missing 5V_S4 on left side? "SD_PWR_EN_LB_L is 0V" Keep in mind what end "_L" means!!!

As I said, that line is good. Check the rest of lines.

Check PMU_ONOFF_L voltage, w/ and w/o keyboard connected. TouchID is embedded into keyboard.

That means you have good contact (o ohm) between pins 43 & 44. You can check directly all voltages and signals on the right side of connector (in schematic I mean). Compare the readings with a good board.

What about PLT_RESET_L behavior? Test with known good BIOS, just in case.

It means to check over the connector, between the same lines. You should get readings close to 0 ohm; if top plate is mounted, of course.

J9600 metal plate is in place? Check continuity left/right for all its lines.

"uc380 1- 0v 3-1,3v 4-0,85v" If you meant UC830, there you have problems. Missing input voltage (3V8_AON) and enable signal.