How to fix iPhone 16 pro or pro max boot looping on Apple logo

How to fix iPhone 16 pro or pro max boot looping on Apple logo
Device	iPhone 16 Pro, iPhone 16 Pro Max
Affects part(s)	Main Logic Board
Needs equipment	Soldering iron, Hot Air Station, Microscope, Tweezer
Difficulty	◉◉◉◉ Specialist
Type	Soldering

Problem description

An iPhone 16 Pro/Max presented with persistent bootlooping on the Apple logo. Standard fixes such as flashing firmware and replacing the battery did not resolve the issue. Further board-level diagnostics revealed a failure on the Analog_BATT_VCELL_POS_CONN line traced back to the U4200 USB/Charging IC. Replacing the IC successfully restored functionality.

apple logo bootloop

Symptoms

• Device stuck bootlooping on Apple logo
• Device does not charge when connected to power
• Occasionally boots up normally but remains unstable

Diagnostic Steps

1. Replace Battery – Installed a known-good battery (no improvement).
2. Flash iOS – Attempted restore/flash in DFU and Recovery mode (device still bootloops).
3. Measure Battery Connector – Found Analog_BATT_VCELL_POS_CONN line showing OL (open line).

   

   battery fpc OL

4. Trace Line – Followed the line from battery connector through PCB layers:
   • OL present even on lower PCB layers → rules out board-layer damage.
   • Only other connection point is U4200 USB/Charging IC.

u4200 ic

Repair Steps

1. Remove logic board and isolate U4200 IC area.
2. Apply flux and controlled hot air rework to safely remove U4200.
3. Clean pads and inspect for pad damage or corrosion.
4. Install new U4200 USB/Charging IC with proper alignment.
5. Reflow and allow the board to cool, then inspect solder joints.
6. Reassemble device partially for testing.
7. Re-measure Analog_BATT_VCELL_POS_CONN at battery connector:
   • Reading returned to normal continuity.
8. Boot test – Device powers on normally, no more bootlooping.

9. 

   phone successfully booted up to homescreen

   Finalize assembly, perform full charging and stability tests.