check resistance between ground & the 6th lines of sim reader to be sure that they are connected ( GND / NC/DATA/ CLK/REST/VSIM) using Diode or Buzzer POSITION on Multimeter.

This is the VDD_Boost IC , check capacitors arround to know which one is shorted with ground , and take it out , befor you have to change the Boost itself , you can easily use a 5 Ampere Power Supply , it helps more— the following pic for IPHONE 7 PLUS VDD disteribution helps you to know where is exactly the shorted VDD capacitor

Better to start to power on using the line No7 / at j2 connecter (short with ground using tweezer), if power on , then change the power switch flex cable , if not working then check line 9 volt , it should be 1.8 v and if not check the line from AMBER PMU to the connector , following pics of mine will help:

check to recharge your battery outside your phone using an external power supply , cause charging battery would not start (by software) if the battery storage less than a certain value !!!

wcdma not active , means you first have to check if it is a good contact between the wcdma antenna pad & the antenna itself - also you check all wcdma filters & ant sw (if there is ) and finally reflow wcdma and its power supply (if there is ), be carefull, not to move any of gsm part to not lose the network completely..

when i repair or change any moile housing ,i always prefer to check my mobile power on/off , using only main board & lcd , whithout even power button , it mean i have to power on mobile using Alternative power point as shown in my own solution pic , it helps so much to know if there is any trouble with the power button flex cable , or with the housing itself , use the shown pic to apply the solution

MY friend , you may have many problems at your phone , first you have to check your battery , or change it with a new one , but befor doing , you have to use an external power supply as a phone charger to check if it is a true , or fake charging ,( if Ampare indicator moves with any value means true , if not move means fake charging ) , you should also check the charging flex cable , and change if needed, i hope this helps you

== Any kind of temperature errors at any kind of mobiles: galaxy, nokia, iphone ,etc often caused by the line of battery temperature(btemp/ at nokia ) (ntc / at iphone ), so , we have first to change charger and also change battery and check battery connector befor we check this battery temperature line to remove capacetors and similar components and to check if the serial elements are ok or need to be change, befor we have to reheat power ic at last , greatings from TAHSEEN TEAM EGYPT bold text