820-4924 MacBook Pro 2015, does not recognize internal SSD

[sekidata]

Board works fine with external drive, but does not recognize internal SSD at all. Apple Hardware Test comes back with error VDH002 ("issue with a storage device"). There was corrosion on the board underside, which I cleaned up and does not appear to be in any SSD-related areas (Thunderbolt, screen backlight). There's also what looks like a small burn hole on the board topside right under the SSD (which leads me to believe that something on the original SSD had exploded).. I scraped the hole area but no vias of importance seem to run through there.

I've never had to fix SSD-relate issues, so any pointers would be helpful.

 

[2informaticos]

Check L3700 first.
Post U3740 voltages, with SSD inserted.

 

[sekidata]

L3700 is at 3.35V.

U3740:
pin 1: 3.43
pin 2: 1.01
pin 3: 3.27
pin 4: 3.43
pin 6: 3.26
pin 7: 0.52
pin 8: 0.00

 

[2informaticos]

"L3700 is at 3.35V"
Both pins?

Check R3701, clean J3700, resolder its pins.
Also check all the caps from PCIE lines (C3710-17).
Just in case, change U3710/11.

 

[sekidata]

Both pins of L3700 are at 3.4V. The SSD definitely has power; it gets warm.
R3701 is NOSTUFF on this model.
Replaced J3700.
Caps C3710-17 are good.
Replaced U3710, U3711, and U3740.

No improvement.

 

[2informaticos]

Check R3702 and R3704-07.

 

[sekidata]

Success! I found an interrupted via next to R3707, which prevented R3707 and the PCIE line from working. Fully functional now. Thank you!