You could remove the backlight driver IC and see if the short persists but IMHO, you should do a bit more probing to be certain. The reason I say this is that every time you apply heat to the board, you are exposing yourself to potential collateral damage. In fact, even applying power to a water damaged board without knowing what condition it is in could lead to permanent damage or data loss.
So before applying power and removing IC’s, it’s a good idea to take a more thorough troubleshooting approach, especially with water damaged phones as there can be multiple failures. Start by probing the main voltage rails, namely VCC_MAIN, BATT_VCC and even PP5V0_USB. If those are shorted, you shouldn’t be applying power until you have done at least some clue gathering. Focus on the corroded areas at first and do a careful visual inspection with a microscope. Any charred caps on the shorted line will need to be removed and tested. At some point though, when a visual inspection doesn’t give you the solution, then you will need to apply power. In doing that, make sure you have a plan and know what you are looking for in advance. You can try freeze spray, rosin or thermal camera to help detect the short. Some are easy to find while others can be excruciatingly difficult.
You’ve already noted heat in the backlight circuit so why not probe the circuit a bit to help you understand what it does and how it works. Start by checking the diodes and do diode mode readings of the anode output and cathode inputs. If they are in good condition (compare to known-good or use a tool like ZXW and start keeping notes for future comparison) then the issue probably isn’t (although it’s not totally excluded) with the backlight circuit. Then check all of the other IC’s that have VCC_MAIN input and do the same. VCC_MAIN shorts are the worst, btw.
You’ll find plenty of videos and comments about replacing this part or that part, 1000% fix, plz bro etc. Those don’t always work because every phone and it’s failure is slightly different. There are trends to keep up on but generally speaking with water damage, it can be anything. I’d rather show you some troubleshooting methods that you can apply even when there are no clues or obvious solutions.
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