820-2936 quarter fan spin

so to start out i dont specialize in mac repair, i mostly work on phones. but a friend of mine had an issue with their macbook so i figured id take a look at it.

so everything is disconnected but the board and dc in board. it shows a green light on the charger and fan starts to spin up then stops. i checked all the main power rails and i found one that isnt right. pp5v_s3 is missing and its weird, when the fan starts to spin it shows 5volts for a split second the 0 again, and if i hook power to the board then disconnect power and test the line is shows as .006 voltage drop in diode mode but if u keep the multimeter probes on it starts to rise until its at like .400 i went over the entire board under a microscope many times and also looked at it with ir camera. i dont see anything that looks terrible. but im stumped and am hoping one of the experts on here can point me in the right direction.