|No power. No charging. Low amperage draw. No short to ground on VDD main, VDD Boost, or 3v0 NAND.
||The charging IC that fails most commonly on this model is the Yangtze IC (U3300). This was the Tigris IC in previous models. It is under the bottom back shield. Use max heat, max air, largest nozzle to remove shield. It requires a lot of heat or tin snips to cut the shield. Be EXTREMELY careful not to float anything or knock off components. Be careful with how much force you use as too much force can flex the board and damage internal traces. The wireless charging IC (Iktara), baseband PMU, and baseband CPU all sit under this shield. Once the shield is removed, this chip is fairly easy to replace and usually fixes the problem.
|SIM Card is not being detected:
||Try a new SIM Reader. On iPhone XR/11/12 (Pro/Max), it is modular and can be replaced. Before assuming it’s motherboard issue, buy a new SIM reader. If this fails, your motherboard is likely defective. Another possibility is a bad baseband CPU. Try to update iOS to the newest version and check under Settings -> General -> About if any modem firmware shows up. If it's not, your baseband CPU is most likely dead and needs to be replaced. Another symptom might be that you have no more reception.
Quick tip: Chinese iPhones use physical dual SIM. You can interchange these SIM readers between models to make dual physical SIM work on any iPhone XR/11/12 model.
|Compass/Gyroscope not working
||If your Gyroscope is not working anymore, the problem might be with a little cable going from the wireless charging coil to the housing. This cable is responsible for proper functioning of the gyroscope. If you damaged this cable while replacing the backcover or battery, you need to replace the wireless charging coil.
|No display. Phone boots but without image.
- Bad Screen (Rule out screen before continuing)
- Pry Damage. It does happen but not common. If a tech is too rough with their pry tool when disconnecting the screen, it is very easy to damage the FPC connectors. The image filters and caps are covered in overfill, so they do not typically get damaged. Can happen though.
- Short on 5v7 line. 5v7 short is the happy, fixable version of this issue. Can be checked using diode mode on the connector. Most of the 5v7 caps are on the back side next to the NAND on this model (weird) but they tend to short from a drop or flexion damage. If you have a 5v7 short, consider yourself lucky.
- Check C5600 cap on PP_CHESNUT_CP. It has no leg on ground. So check to see if it has continuity across it. If it does, replace it.
- A cap should NOT have continuity across it.
- Chesnut/CPU issue (not happy/fixable version of repair). It is very common for this model to have no image randomly with no damage or no 5v7 short. Usually, heat on the shields or replacing Chesnut resolves the issue but not for long...most common visual issue is the CPU shield being broken in the bottom right corner by the WiFi IC. This happens from a hard drop or flexion damage. Replacing chesnut is a placebo because it is basically just heating broken traces under the CPU. This temporarily restores image, but it will come back for warranty. True fix is to reball the CPU, but it is not practical. Usually, this is a data only scenario to avoid reworks/warranty repairs. For Data Recovery only, you can temporarily clamp the CPU down & get image long enough to connect to iTunes or 3U tools and run a backup.
|Stuck in DFU mode
Flashes successfully with an update or restore but goes back to DFU mode.
- Screen shows no image and pulls 0.45A via USB charging
- Does not appear to boot
- Prompt to boot on DCPS, shows it hangs around 45mA draw
- Connect to PC and it's in DFU mode
- Flash an update or restore & it goes through 100% with no errors but goes back to DFU mode
- Check R0601 at the corner of NAND.
- This resistor connects PP1V8_IO to SPI_AP_TO_S4E_MOSI_BOOT_CONFIG1
- Clean the underfill around it & poke it hard.
- If it breaks, it must be replaced.
- Value is 4.7ohms
- After replacing it, the phone will no longer be in DFU mode & boot right up.
|Phone freezes at the last digit of the pin code
- Phone boots fine
- Type in your pin code & at the last digit, it freezes, keeping that digit highlighted for about 30-60 seconds
- Then the screen restarts and you're back at the pin code screen.
- Check NFC (U_NFC_S) above CPU
- It most likely has a hairline crack & requires to be replaced.
- Once replaced, the phone will go through a "swipe to recover" screen in most cases, where you put in the pin code, it loads a white "Attempting Data Recovery" screen & takes about 10-20 minutes.
- This is basically the operating system rewriting the NFC chip, so it can unlock.
- Then, the phone will work fine afterwards
Heat above the CPU
- You get 1A or higher current draw before prompt to boot on DC Power Supply
- You feel heat above the CPU
- You either have a cracked Speaker Amp (U5002)
- Or a shorted cap on PP_SPKAMP_TOP_VBOOST
- Use a Thermal Cam or Freeze Spray to pin point the root cause of the short
- Phone does not boot using power button nor plugging in the charger
- Phone charges at 0.013A
- On DC Power Supply, it draws 82mA before prompt to boot
- The most likely culprit is Yangtze.
- Replace Yangtze (U3300)
- It is the "Charging IC" for this model
- After replacing, check if the 82mA current draw before prompt to boot is cleared, to confirm the issue is solved.
- In some cases, a liquid damaged ear speaker flex can cause no charging.
- Try testing with the ear speaker flex unplugged.
Please Note: The shield covering Yangtze is very tough to remove. It is recommended to add 138C low melt solder to all the solder joints around the edges, to make it a little bit easier to remove.
In the process, you may float Baseband or WTR that is under the shield. & cause baseband issues.
- Shows apple logo for about 5 seconds, then blank, then apple logo, then blank
- Sometimes it shows a green flash for a second
- If you try to flash an update or restore, it fails right away with an Error 4013
- If you flash on 3u tools, it fails at 19%
- Step 1 in this case is always unplug all the flex cables.
- Ideally test the board with known good Screen, Battery & Charging Port.
- If it boots, then one of your flexes is the cause.
- 99% of the time, it is the ear speaker flex. The Flood Illuminator and/or the ALS has liquid damage.
- The ear speaker flex is paired to the logic board for Face ID.
- If you want to keep Face ID, you'll need to repair the flex. If Face ID is not important, then you can just replace the flex.
- To repair the flex, you'll have to desolder the component & clean out all the corrosion, then place them back.
- If the corrosion is too severe & it damaged the flex, then you'll need to swap the Flood Illuminator and ALS to a new flex, otherwise, you'll lose Face ID.
- In some cases, another flex can cause this issue like a bad charging port.
- In this case, just replace the flex
Please Note: If the phone is stuck in Recovery Mode because it failed at the Error 4013, you have 2 options
- Kick the device out of Recovery Mode using 3U Tools. In the main screen of 3U Tools, you'll see a button that says "Exit Recovery Mode"
- You can attempt another update or restore.
Assuming you fixed the root cause of the bootlooping issue, the above 2 options should get you a working phone.
If it still fails at 4013 or still bootloops, then you haven't solve the issue.
|No Front Camera
- Rear cameras work, but when you switch to front cam, it doesn't work
- Front camera shows black screen
- Try a new front camera. Since the front camera assembly is 3 pieces, you'll lose Face ID if you replace all 3
- Make sure to UPDATE after replacing the front camera. It won't work just by replacing it.
- If that solves your issue, then the front camera is bad.
- If you don't want to lose Face ID, you can attempt to get the front camera only out of the metal housing to replace it & keep the IR cam & Dot Projector original.
- Diode mode the front camera connector & check for any issues
|No Rear Camera
- Rear camera doesn't work. Just shows black screen
- But front camera is working
- First step would be to Diode Mode the Rear Camera Connector
- Check for any shorts or Open Lines (OL)
- Check the LDO U1601. This is a power rail for the camera
- IMPORTANT: Check orientation of the LDO from the actual board. ZXW shows Pin 1 incorrectly, so orientation is wrong.
- See if this LDO is loose or broken.
- Or just try replacing it & see if rear camera starts working.
Take notice of the orientation dot
|Phone Shutdowns immediately after entering the lock code.
||if the device has a broken back, it is possible that the wireless charging coil is short to ground. (this may be the same for any iphone with a charging coil. This also can be caused by water damage to the ambient light sensor.
To test this, unplug the connector and power the device, and log in. If device stays on, then the component on that flex is the culprit, replace the coil or earspeaker flex to fix the issue ( note: face id is tied to the ambient light sensor and possibly requires resoldering)