Zubair,
it seems to be Someone misguided you. finding U2 on 5C like you waiting for jack sparrow in black sea! (i was kidding :-) )
Okey lets begin to troubleshoot your device,
**Keep in mind, before touch power ICs you should check few steps
1) Check whether liquid contacts indicates triggered, check any sign of liquid damages in the logic board
https://support.apple.com/en-lk/HT204104
(logic board having triggers too )
2) Should check RF amplifier short circuit (4G/3G/2G and Wifi)
Charge the phone in off mode and turn on the flight mode / turn off the wifi and check whether standby time increase?
if you do in professional way : Connect power supply via battery connector and can be measure the power consumption step by step turning on connectives
3) Check any sign of burned components around PM8018, any corrosion?
4) Remove the Display touch pad FPCs. turn on the logic board and check either heating it like earlier
5) if No, check the LCD back light contacts resistance and drive voltages
6) If yes, Replace PM8018 : BGA reworking skills required.
if you have good oscilloscope i can help to find exactly where is the fault coming from.
Hope this answer help you to get it back to working in order
Cheers!