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U8500 power input and enable signal drop?

"Remove R8164-8, one by one..." Check in SMC bypass mode.

The machine can't boot without NAND!

Remove R8164-8, one by one, until find where the problem comes from. Keep R8167 in place.

If UC710 gets enable, it should work...

If you get correct 3V8_AON, Q5840 should be good. Sorry, I understood wrong your mention about NANDs. But many times sudden death is caused by faulty NANDs; no need to be shorted to ground.

Once you connect something mor eon same line, diode mode readings should drop a bit. Unless you've checked in reverse way. You¡ve said U8500 gets power and enable; it should generate 5V_S0SW_LCD. Just in case, replace C8509; also try another U8500 chip.

Do you get voltage on all big coils (apart of CPU core)?

You've said UC710 gets power and enable; it should generate 3V3_S2. Just in case, replace CC714; also try another UC710. Did you check XWC711 too?

4 ohm is good enough. Did you get replacement CD3217 chip from same board model and position?

You don't need an o-scope to diagnose the motherboard. Only to see the signals on mentioned coils and understand why ALWAYS MUST check DC voltage on the output pin! Where did you get the replacement NANDs? Are you sure you didn't damage anything in the process? Please, don't quote an entire...

That doesn't mean the trackpad works...

"0.144V which should be 0.150V" Do you really think that is a BIG difference? Checking on your board with different multimeters, you will get different readings. BTW, stop checking DC voltage on the input side of the coil from buck converters. Compare input/output with an o-scope and you will...

Remove Q8150 and check again ALL_SYS_PWRGD.

High value resistors can't be properly checked onboard. Move them a bit, letting one pin free; this way makes the test easy. "Traces look fine" Tested in buzzer mode (until UC710)? You can test removing CC719/20; possibly corroded.

Ohm scale is used for very low readings; usually under 0.010 reading in diode mode.

3V8_AON should be stable. Check diode mode to ground there; wait 10-20s after power is removed.

If you replaced the NANDs, machine should automatically enter in restore mode.

Test with known good audio jack flex.

"5v_s0sw_lcd - 1443" Not sure what kind of reading is that. Diode mode should be good enough to check; with LCD connected.