Macbook Pro Retina 13 Inch no power

Well, it looks obvious the display connector is dirty, it may leads to no power, cleaned it, reflowed it, still nothing.Ah-ha! Found some more corrosions on board. It is something todo with PP3V3_S4, it’s no good if it is grounded. measure it, confirmed it is only 0.44V rather than 3.3V

The rest is easy, remove it, clean it, replace it. Done.