MacBook Pro A1706 Question mark folder or SSD not recognized repair

MacBook Pro A1706 Question mark folder or SSD not recognized repair
Device	MacBook Pro A1706
Affects part(s)	Motherboard
Needs equipment	multimeter, soldering iron, soldering station, thermal camera
Difficulty	◉◉◉◌ Hard
Type	Soldering

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Problem description

Question mark folder, no external boot possible & Recovery does not work on A1706 MacBook

Figure 1

Symptoms

• Question mark folder
• No external boot possible
• Recovery does not work

Solution

Check R9350

• Examine R9350 (PICCOLO_IUVD) on the board
  • Check if R9350 is no longer soldered to the board.
  • Look for any missing pad for pin 1 (PPVIN_2V7NAND_LB). Refer to Fig 1 for visual guidance.
• Inspect the area near R9350
  • Examine the trace coming out of Terminal 1 of R9350.
  • Be cautious about the neighboring via, as it can break the trace.
• Measure the resistance of R9350
  • Ensure it is within the specified range.
• Look out for potential trace issues
  • Sometimes, the neighboring via can damage the trace, resulting in connectivity issues. Check for broken traces and continuity problems.
  • Example of a broken trace (Fixed by running a wire to replace the broken trace)
  • Be aware of potential bad probe points, which may look good at a cursory investigation

Check the Piccolo circuit

the Piccolo circuit can be sensitive to any sort of water damage in its vicinity.

• Probe inductors near the Piccolo chip. If they are shorted, replace the Piccolo chip. Injecting 1.3 V on these inductors usually won't give you a strong hotspot.
• In cases of no liquid damage, if the SSD is dead, It's probably unfixable.
• Measure C9416, Q9401, or U9400 for short circuit, it often happens due to issues with U9400 circuit
• In rare cases, there may be no damage in the R9350 area, but the TP above R9350 may lack PPVIN_2V7NAND_LB. Check the continuity between that TP and pin 43 (PPVIN_2V7NAND_LB) of J9600. In such cases, consider running a jumper wire from the closest source of PPBUS_GSH (pin 1 C6582) to the testpad after which, the SSD should now be detected.
  • After inspection and not finding any breaks in that PPVIN_2V7NAND_LB line, I deliberated on where to best access PPVIN_2V7NAND_LB from. I ran a jumper wire from pin 1 C9400 (PPVIN_2V7NAND_LB) and conformal coated that enameled jumper wire and considered it a viable repair.
• In other situations, a damaged trackpad cable can short PP3V3_S4_TPAD. This line goes through R5650 and then to R8901 as PP3V3_S4, and leaves as STORAGE_EN to go to J9600 lifeboat connector. It continues as STORAGE_LB_EN and goes to U9300 as its EN line. U9300 is the PMIC for SSD. Replacing the trackpad cable may resolve the issue.
• If the issue persists, and there was a history of liquid spill on the keyboard, disconnect the keyboard as it may be causing the problem.