IPhone 14 Pro Max No Touch

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IPhone 14 Pro Max No Touch
Device
Affects part(s)
Needs equipment
Difficulty
Type

Problem description

iPhone 14 pro/ pro max boots normally but touchscreen does not respond at all. Display shows image, but there is no touch input on the entire panel. Replacing the screen does not fix the issue.

Symptoms

• Touchscreen not responding at all
• Screen replacement does not fix the problem
• GR on display connector is normal

Solution

The problem generally is due to a faulty capacitor that is placed on the touch boost line. Replacing the capacitor C9201 fixes the issue.

Bad Cap

The bad capacitor

Diagnostic Steps

1. Check diode values on the connector, if you see any unusual reading trace it or else continue to the next step if all diode values are good.

   

   Diode value

2. Check for voltage on the PP_5V1_TOUCH_VDDTX_S2:
   • You cannot normally check voltage on this line
   • In order to check voltage on this line you have to manually enable the ic by giving it an enable signal and here is how to do it:

     

     Schematic

     • Plug the DCPS cable/ battery to the phone 3.8-4.2 volts
     • Inject 1.8v at lowest possible Ampere on pin #31(according to JC DRAWING) to enable the LDO output

       

       Inject Voltage

     • Check the output voltage on pin #44(according to JC DRAWING)

       

       Touch Boost Output

     • If you get no voltage output then proceed to the repair steps
       

Repair Steps

1. Split the board in half
2. Check the capacitor C9201, if shorted remove it

   

   Bad Cap

3. Recheck for shorts
4. If short is cleared then proceed to replace the cap
5. In some rare cases of which short is not cleared:
   • You have to replace the u9200
   • Check diode value under the ic before replacing it

     

     Touch ic Diode

   • Replace the ic and the capacitor
6. Test the touch function, it should be restored.