iPhone 8

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Models
Model Type Modem Region
A1863 8 Qualcomm Global
A1905 8 Intel Global
A1906 8 Intel Japan
A1864 8+ Qualcomm Global
A1897 8+ Intel Global
A1898 8+ Intel Japan
Problem Solution
No Power — Pulls ≈2 A or more before you prompt to boot on DC power supply Do a full visual inspection of the board and check for water damage under the stickers on the back. Remove the foam around the connectors to get a better look at everything. You're looking for any signs of corrosion on or around components and ICs.


If there is no water damage, is is most likely a shorted capacitor on any of the below lines:

  • PP_VDD_MAIN — This is the most likely line to be shorted
  • PP_VDD_BOOST — This line is usually shorted when it's not VDD MAIN
  • PP_DISPLAY_BL_ANODE or PP_DISPLAY_BL34_ANODE — Sometimes the backlight circuit has a short and causes the same symptoms
  • PP_SPKRAMP_TOP_VBOOST — This is a bit rare but it does happen


You'll need to inject voltage (4 V / 2 A) directly into the line you measured as short and use freeze spray (see here https://youtu.be/3MtLSQJvQxI) or thermal camera (see here: https://youtu.be/fkd4iDjgfvc) to spot the capacitor that is shorted.

In these cases, you can just remove the shorted capacitor and not replace it. The device will function normally with no negative effects.

Replacing it means you are adding more heat to the board to reinstall it, which increases the risk of something going wrong.

If you have a case of water damage, then you'll have to pay attention to the spots on the board where there's signs of water damage.

Often, you'll find corrosion on capacitors but also under ICs.

Common ICs and areas to have corrosion and cause a VDD MAIN short:

  • Under BBPMU and around it, like Capacitors: C303_E
  • Back top "arm", like C4190, C4191, C4195, C4196
  • Above and next to WiFi (WLAN_W), like C7608_W, C7609_W
  • Front Top above CPU, like C3790
  • Sometimes, you'll find a loose screw shorting TP0526 to ground.
    • This is a Test Point next to the SIM Card slot, opposite side of the CPU shield, underneath the sticker.


You'll need to visually inspect these areas to see if they're liquid damaged


Please Note: If you are using a DC power supply to inject voltage through the battery connector, like using an iPower Pro or DT880 (see here https://youtu.be/rawjB9yxe1A), be aware that the Tigris Mosfet Q3350 will heat up instantly. This is because the battery connector line PP_BATT_VCC connects to PP_VDD_MAIN through it, which creates lots of heat. Q3350 itself does not have a connection to ground, therefore, it's impossible for it to be shorted.

No Power — After prompt to boot on DC power supply, current jumps back and forth from 0 A to 320 mA, then 0 A to 1.4 A, then 0 A to 500 mA, and so on

Symptoms:[edit | edit source]

  • No current draw before prompt to boot on DC power supply
  • After prompt to boot, you see the current jump quickly between 0 A and various values, like 0 A > 320 mA > 0 A > 1.4 A > 0 A > 500 mA

Solution:[edit | edit source]

  • Check for shorts around NAND
  • Usually you'll find these lines with a shorted capacitor:
    • PP3V0_NAND
    • PP0V9_NAND
    • PP1v8_IO
  • If so, find the shorted capacitor by injecting voltage


Please note: PMIC (U2700) will often show lots of heat if you're testing with the DCPS connected through the battery connector but it's not the cause of the short. The short is at the capacitor next to NAND, but since you're connected to the battery connector, the current has to flow through PMIC to get to the short cap, hence the PMIC heats up.

Another Possible Cause:[edit | edit source]

Sometimes, you'll see this same behavior when PP1V8_S2 or PP1V1_S2 is shorted. If this is the case, you'll need to check for heat above the CPU. If you find PP1V8_S2 or PP1V1_S2 is shorted and find heat above the CPU, then it's a RAM short.

You'll need to replace RAM to solve it. This a very advanced repair and should only be done by those who've mastered this repair. It's very easy for things to go wrong and damage the CPU.

Developed the issue with the phone stuck in "Searching" or "No Service" on its own (no previous repair attempts)


Baseband Issue

Symptoms:[edit | edit source]

  • If no previous repairs attempts were made on the phone, but has these symptoms:
    • With no SIM Card installed, the phone is always "Searching..." or "No Service".
      • A working phone will show "No SIM" with no SIM Card installed.
    • Dial *#06# in the phone app, and nothing happens
      • A working phone with no Baseband issue, will make the IMEI pop up.
    • If you go to Settings > General > About > Model Firmware is blank

Solutions:[edit | edit source]

Intel Model[edit | edit source]

  • Replacing BBPMU_K should solve it.
    • Part# PMB 6848

Qualcomm Model[edit | edit source]

  • Replacing U_PMIC_E (aka BBPMU) should solve it
    • Part# PMD 9655


Please note: If you attempt the above repairs, but it's still stuck in "Searching..." or "No Service", then flash an update (DO NOT RESTORE). This can sometimes solve the issue. Not sure why it is needed sometimes.


If a phone with a baseband problem is restored, then the iOS software will "erase" the IMEI (baseband info) in the phone and will require the board issue to be fixed, then restored again, so the software will bring back the IMEI.

If you restore, and still has no IMEI, then a baseband/board issue is still present on the board. That will need to be fixed, then restored again.

Unable To Activate

Symptoms[edit | edit source]

  • If a phone has been restored and stuck at the Hello screen
  • You try to activate and get the "Unable To Activate" screen

Solution[edit | edit source]

There are 2 potential causes

  1. Baseband issue. See above Baseband Issues for solutions
  2. NFC issue. You most likely need to reball or replace NFC_RF
No Backlight Or Half Backlight (Dark Spot in a corner)

Diagnosing[edit | edit source]

iPhone 7 with No Backlight
iPhone 7 with No Backlight

You'll want to check these first to confirm you have a board issue:[edit | edit source]

  • Get a known good screen — Helps validate that you have a board issue.
  • Check USB Charging Current — If an iPhone shows proper charging current (≈1 A via USB or more), then mostly likely the device is alive.
  • Listen to for any sounds or vibration — Helps confirm if the phone powers on.
  • Turn off the phone, then plug in the charger and use a flashlight onto the center of the screen, to look for the Apple logo — This helps confirm you are getting image, but no backlight.
  • Check for water damage. Often times, the backlight circuit gets hit the hardest in water damage cases.
  • TEST WITH CHARGING PORT UNPLUGGED. Seen a few where liquid damage at the taptic engine (which connects through the charging port), will cause no backlight.
    • In this case, replace the charging port and/or taptic engine.

Solution[edit | edit source]

In most cases, no backlight is caused by blown filters on the backlight circuit.

Most commonly it's due to these Filters


iPhone 8

  • R5735
  • R5733
  • R5734

iPhone 8 Plus

  • R5730
  • R5733
  • R5735
  • R5731
  • R5732


You'll need to use Diode mode on your multimeter to find the blown filter. (see video for the full process of diagnosing the backlight: https://www.youtube.com/watch?v=K-FFSMiHXPw)

Since backlight comes from the LCD connector, this is the connector you want to check the diode mode readings. Essentially, you're comparing the diode mode values of a known good board vs your problematic board. Most boardview software, like ZXW, will provide the known good diode mode values and you can use that as reference. Expect to see a small ±5–10% variance of what you get.

With a backlight issue, you should find a pin on the LCD connector to read OL, when it should be giving you a diode mode reading. This line with the OL is what you want to investigate further.

These are the lines to expect to find an issue:

  • PP_DISPLAY_BL12_CAT1_CONN
  • PP_DISPLAY_BL12_ANODE_CONN
  • PP_DISPLAY_BL12_CAT2_CONN
  • PP_DISPLAY_BL34_CAT1_CONN (iPhone 8 only)
  • PP_DISPLAY_BL34_ANODE_CONN (iPhone 8 only)
  • PP_DISPLAY_BL34_CAT2_CONN (iPhone 8 only)


Also, sometimes, you can get lucky and visually spot the blown filter, but it's recommended to use your multimeter to confirm it's bad, as well as check the rest are good.

  • A good/working filter will have continuity across it and will have the same diode mode reading on both sides
  • A blown filter will not have continuity across it. In diode mode, you'll find one side has a diode mode reading and the other side will have either OL or a reading that is a larger value than what it should be.

The replacement filter should be the same value of the original. You can see the values in the schematic or boardview software like ZXW.


Please Note: Never use a jumper wire as a replacement for a filter. This can permanently damage the phone if a surge in current occurs and there's no filter to protect the circuit.

Once you replace the filter, check that you be able to diode mode the connector again and find that the pin that was reading OL, is now giving you a proper reading.

Now you can test again and confirm the backlight is working again.

No Image — Turns on, but nothing displays on the screen. You'll want to check these first to confirm you have a board issue:
  • Get a known good screen — Helps validate that you have a board issue.
  • Check USB charging current — If an iPhone shows proper charging current (≈1 A via USB or more), then mostly likely the device is alive.
  • Listen to for any sounds or vibration — Helps confirm if the phone powers on.
  • Turn off the phone, then plug in the charger and use a flashlight onto the center of the screen, to look for the Apple logo — This helps confirm you are getting image, but no backlight.
  • Check for water damage. Often times, the backlight circuit gets hit the hardest in water damage cases.
  • Plug into computer and see if iTunes or 3uTools detects the device in DFU mode. When an iPhone is in DFU mode, it won't display anything on the screen. Sometimes it display an Apple logo for a split second, then blank screen and backlight ON

Troubleshooting Steps and Solutions[edit | edit source]

Here's are 2 walkthrough videos:

LCD Connector:[edit | edit source]

Diode mode the LCD connector (J5700) and check for any shorts (0.000 V) or OL on a line where there should be a reading (≈200–700 mV).


Most commonly, you'll find the filter FL5705 (240 Ohm, 0201) has been pry damaged, causing no image.

Replace it & it should solve it.


Otherwise, you'll find one these lines shorted to ground:

  • PP5V7_DISPLAY_AVDDH_CONN
  • PP5V7_MESON_AVDDH_CONN
  • PN5V7_DISPLAY_MESON_AVDDN_CONN

If shorted, you'll need to inject voltage to find the shorted capacitor.

Please note: Inject no more than 5.7 V but it is recommended to inject like 2 V or 3 V and see if that's enough to find the short. Injecting 5.7 V will inject too much power too quickly and cause the heat to spread really fast and hard to pinpoint the shorted capacitor.

Sometimes, you'll find an OL reading at PP1V8_LCM_CONN. If so, find FL3906 and check for pry damage or blown filter. Replace if you get a diode mode reading on one side of the filter, but OL on the other. Both sides of the filter should give you the same diode mode reading.

Chestnut (U5600) — Image IC[edit | edit source]

If diode mode reading at the LCD connector is good, check Chesnut (U5600), which is responsible for image.

Check C5600 for continuity across it. It should not have any. If there is continuity, replace it.


Check if there's any water damage under Chesnut. Lift the IC and see if any corrosion is present. If so, clean corrosion and replace Chesnut and test again.

If still no image, diode mode the pads underneath Chestnut and check for any shorts or OL on a line where there should be a reading.

If you find a shorted line, track down the shorted capacitor by injecting voltage

If you find an OL where there should be a reading, follow the path of the line and diode mode every at every point. Find the point where the diode mode reading reappears. That should be where the line is disconnected and you'll need to replace the component that disconnected the line, usually a filter.


If no abnormal readings under Chestnut, just replace Chestnut and test again.

No Touch — Phone turns on but touch doesn't work Symptoms:
  • With a known good screen, phone turns on but no touch


Troubleshooting Steps and Solutions

  • Diode mode the LCD connector (J5700) and check for any lines that are OL or 0.000 V (shorted).
  • In most cases, you'll find pry damage near the connector, causing damage to a filter or resistor. Commonly damaged:
    • FL5776
    • FL5762
    • RR5772
  • If you find an abnormal diode mode value, see if the name of the line mentions the word "touch. This will help assure you that you're looking at the right spot
  • Follow the path of the abnormal value by doing diode mode readings on every component in the path, to see where the correct diode mode reading is located. That will point you towards the failed component.
    • For example, if the top side of FL5776 gives you OL, but the bottom side of it gives you 0.442, then you found your failed component.


Another solution:

  • If you found the diode mode readings are all normal, then most likely it's a connector issue
  • Find the 4 ground pins on the LCD and Home Button connectors and use fine tip tweezers or an Xacto blade to bend them outwards.
  • Refer to the example image below
  • Pull these corner ground pins outwards to fix no touch
  • Usually this issue is caused from too many screens being unplugged and plugged in, causing those pins to be pushed outwards
  • Or from someone plugging in a 8/8P screen into a 7/7P board or vice versa
  • If still no touch, you can try replacing the LCD connector to see if that solves it.
iPhone 8 Plus - Grayed Out WiFi This issue is mostly present on iPhone 8 Plus, not so common on iPhone 8.

Symptoms:[edit | edit source]

  • WiFi toggle button is grayed out in the settings
  • WiFI button is not clickable in the control panel

This means there is a board issue. It is not an antenna or flex issue, as they don't cause the button itself to be grayed out.

An antenna issue would cause the signal to be weak, like no bars or just 1 bar.

Solution:[edit | edit source]

  • In most cases, there are ripped pads on the corner, under the WiFi (WLAN_W) chip.
  • Pins 19, 20, 22 and 23 must be jumped to their respective traces.
  • For Example:
    iPhone 8 Plus - 4 Jumper solution for Grayed Out WiFi
    iPhone 8 Plus - 4 Jumper solution for Grayed Out WiFi
  • Once the jumpers are in place, use UV mask to cover them, to prevent any shorting/bridging/movement
  • Reball the original WiFi IC & place back.

See full repair tutorial here: https://youtu.be/eVmKNJ7nsgI


If the WiFi chip ends up having torn pads, you must replace the WiFi IC.

For this, you'll need to also unbind (aka unlock) the WiFi chip via the NAND.

The NAND is what has the paired info for the WiFi chip.


You can unlock the WiFi using the iRepair P10 using Purple Mode to reprogram the NAND & unpair the WiFi chip.

It is done via USB. No need to desolder the NAND.

Bootlooping — Error 9 You'll want to check these first to confirm you have a board issue:
  • Get a known good screen, charging port and battery — Helps validate that you have a board issue.
  • Get a known good OEM iPhone cable
  • Flash with 3uTools using Easy Flash
  • Flash with 3uTools using iTunes Flash

Solution:[edit | edit source]

If 3uTools Easy Flash gives you a failure at 19% or 20% and 3u Tools iTunes Flash gives you Error 9, then the issue is NAND. You'll need to replace NAND. NAND is the memory/storage chip.

Compatible NANDs[edit | edit source]

For iPhone 8 and 8 Plus, you can use the NAND of any of the following devices interchangeably:

  • iPhone X
  • iPhone XS
  • iPhone XS Max
  • iPhone 11
  • iPhone 11 Pro
  • iPhone 11 Pro Max
  • iPhone SE 2 (2020)

NAND Programming Process[edit | edit source]

Requirements

In order to successfully replace the NAND, you'll need the following from the original device or NAND and write it to the replacement NAND, otherwise it won't activate.

  • SN (Serial Number)
  • WiFi Mac Address
  • BT (Bluetooth) Mac Address

It's also recommended you set these to the correct values, but technically will function fine if you put different values

  • Region (USA, China, Japan, UK, etc.)
    • LL/A is for USA
  • Color (Black, White, Rose Gold, Red, etc.)
    • This sets the boot up color of the screen. iPhones with a white screen will boot with a white background and black Apple Logo and vice versa for black screen devices.

Tools[edit | edit source]

You can use any NAND programmer that supports iPhone 8/8P

JC P11F seems to be the most popular.


iRepair P10 is another option, that does NAND programming via the lightning port and uses the available "Purple Mode" exploit.

But is only supported by iPhone 8, 8 Plus and iPhone X.

What if I don't have the original NAND data?[edit | edit source]

You can get the required NAND info from above, by reading the original NAND from the device.

In most cases, you should be able to read the NAND data.

If it can't, you'll need to find it elsewhere

  • GSX report (You'll need to find someone who offers this service)
  • MagicCFG Recovery (requires Jailbreak)


Sometimes, the GSX report service is not available.


Without the original NAND data, you'll never be able to activate the device unfortunately.


Using MagicCFG Recovery

First, you'll need to install the replacement NAND, with any generic data filled in for SN, WiFi, BT, etc..

Then restore the phone

Then you need to jailbreak the device with Checkra1n

After, run the MagicCFG Recovery tool, which will capture the SN, WiFi/BT Mac addresses.

Then go back, read the NAND, edit the SN, WiFi, BT addresses and write them again into the NAND

Then restore one more time

Now you should be able to activate the device.

Not Charging after screen repair

Stuck at 0% battery

Random Restarting (Usually after 3 minutes)

You'll want to check these first to confirm you have a board issue:
  • Get a known good screen, charging port and battery — Helps validate if you have a board issue.
  • Get a known good OEM iPhone charging cable and brick.

Symptoms[edit | edit source]

  • Phone will fully boot up and get to the home screen but after about 3 minutes, it will just spontaneously restart
  • Sometimes the phone's battery is dead, but it will just bootloop forever.
  • Or sometimes it will boot to the home screen then instantly restart
  • You'll notice the battery level is sporadic (value constantly changes) or stays at 0% or 1%, even if battery is fully charged
  • You see it's not charging, where USB meter charging current is jumping all over the place, instead of a 1+ A current draw via USB.
  • In Settings > Battery > Battery Health, it says "Service" and no battery health percentage.
  • In 3u Tools, it shows no battery data.


If you see any or all of the symptoms above, it is usually a sign the phone cannot "talk" to the battery.

These 2 lines are responsible for transmitting data from the battery to Tigris to the CPU.

  • I2C0_SMC_BI_GG_SDA_CONN
    • Connects to the Q3200 Mosfet
  • I2C0_SMC_TO_GG_SCL_CONN
    • Connects to the Q3201 Mosfet
  • Q3200/3201 Part Number: RV3C002UNT2CL
    • Can be purchased from Digikey, Mouser, etc.

Solutions[edit | edit source]

Battery connector:

  • In some cases, the battery connector is warped or damaged
    • You can visually inspect the small center pins of the battery connector. If they look like they're "pushed out" and hidden under the plastic of the connector, you can try pushing them back out with a tool
    • If the connector looks smashed or missing plastic, then replace the connector
    • Or you can replace the battery connector itself.


Pry Damage after screen repair:

  • If it happened after a screen repair, then most likely one or both battery mosfets (Q3200/Q3201) got damaged.
    • Diode Mode the battery connector. The 2 small pins are the data lines that connect to the mosfets.
    • If one or both small pins read as OL, then you have a damaged mosfet.
    • If you have no ripped pads, replace the damaged mosfet,
      • Then diode mode the battery connector again to make sure you have a diode mode reading again (~.665v)
    • If you do have ripped pads, you'll need to run jumpers for the appropriate pin(s).
    • Below shows where each pin connectors to.
    • In red, is the top pin. Run jumper from A to B.
    • In blue, is the bottom pin. Run jumper from C to D
      iPhone 8 battery connector to mosfet connections
      iPhone 8 battery connector to mosfet connections
    • Video Example:


Something Else:

  • If the above doesn't solve it, then try replacing Tigris.
    • Please Note: On older iPhones, it is known that Tristar will cause charging issues & replacing it will solve it. For iPhone 8/8P and newer, that chip is now Tigris that fails & requires a replacement
  • If this also doesn't solve it, it could be Hydra or another line under Tigris or Hydra having an issue.
    • You'll need to diode mode each pad under Tigris and Hydra to see if you can find an OL or a short, causing the issue.
      • If you find a shorted line, track down the shorted capacitor by injecting voltage
      • If you find an OL where there should be a reading, follow the path of the line and diode mode every at every point. Find the point where the diode mode reading reappears. That should be where the line is disconnected and you'll need to replace the component that disconnected the line, usually a filter.

Final Testing[edit | edit source]

  • Run the stopwatch app and see if it can run for longer than the 3 minutes that it was rebooting at
  • Play a 1hr Youtube video to see if it can play it continuously
  • Check the USB charging current
  • Check the Battery Health in the Settings
  • Check if the battery level is showing accurate battery levels.
Speaker button is grayed out during phone Please Note: Although the symptoms are similar to the iPhone 7/7Plus Audio IC failure, the solution is different.

Symptoms:[edit | edit source]

  • When you make a call, the speaker button is grayed out & you cannot click it.
  • When trying to record a Voice Memo, it won't record.

Testing and Solution:[edit | edit source]

  • Unplug the Front Facing Camera, then test again
  • If the issue is solved, then plug in a new front-facing camera flex cable and try again
    • Please note, replacing the Front Camera flex on iPhone 8 & 8 Plus, will make you lose True Tone.

Explanation:[edit | edit source]

Usually this is caused by the ALS or proximity sensors getting some corrosion from liquid damage.

It's easier to just replace the part, but sometimes, you can clean off the corrosion with a toothbrush and isopropyl alcohol and get the flex working again.

Phone will restart when you make a phone call

Symptoms:[edit | edit source]

When you make a call, the phone will instantly restart or shut off.

Testing and Solution:[edit | edit source]

  • Unplug the Front Facing Camera, then test again
  • If the issue is solved, then plug in a new front-facing camera flex cable and try again

Explanation:[edit | edit source]

Usually this is caused by the ALS or proximity sensors getting some corrosion from liquid damage.

It's easier to just replace the part, but sometimes, you can clean off the corrosion with a toothbrush and isopropyl alcohol and get the flex working again.

Stuck in DFU Mode — Error 4014

Symptoms:[edit | edit source]

  • You get no image from the screen
  • You plug into computer and iTunes/3U tools detects it in DFU mode
  • If you try to Update or Restore, you get these results:
    • iTunes Error Code: Error 4014
    • 3u Tools Easy Flash: Fails at 19%

Cause:[edit | edit source]

  • Error 4014 is usually "NAND not detected".

Solutions:[edit | edit source]

  • Check the caps around NAND to see if they're shorted.
    • If there's a short, remove the shorted cap and try to boot the phone up.
  • If no short, pull the NAND and connect it to the JC P11F NAND programmer and see if it's readable
    • You can refer to this video for how to use the P11F Programmer: https://youtu.be/J6n2Bj7sG5A
    • If it doesn't read, the NAND is dead and needs to be replaced
    • If it does read a NAND, then you can reball NAND and install it again. The phone should boot right up.
Home Button will rapid click when you press it Please Note: iPhone 8 and 8 Plus Home Buttons are paired to the phone, so you cannot replace the home button. If you do, the home button will completely stop functioning. No click and no Touch ID.

Only Apple, AASP, and IRP are able to replace home button and get home button function and Touch ID function working.

Potential Causes:[edit | edit source]

  1. If this occurred after a screen replacement, check the home button screen flex to see if there are any tears on it
    1. If you find tears, replace the screen
      iPhone 7 Screen - Home Button Flex
  2. Try placing the original home button into another known good screen to check if issue persists
    1. This will validate if the problem is in the screen somewhere.
  3. Visually inspect the home button flex itself for any small tears
    1. If you find tears, you'll need to run jumpers to reconnect any broken traces. You can refer to ZXW. Select "Phone8P_QCOM+Touch". This works for iPhone 8 and 8 Plus.
  4. Visually inspect the small flex in the home button (the one that folds over). It often cracks and can cause this issue
    1. If so, you'll need to run jumpers to reconnect the broken traces. This small flex has about 4 lines that need to be jumped. You'll need to scrape the exterior layer and expose those 4 traces.
    2. See video tutorial on how to fix the small flex with jumpers: https://youtu.be/INTSNTWvRxQ
  5. Visually inspect the small IC on the home button flex (Turtle IC U10) for any small cracks or small chips
    1. If so, you can replace the Turtle IC U10. It is not paired to the phone and can be replaced.
    2. Turtle IC is the same for iPhone 7, 7 Plus, 8, 8 Plus.
  6. Visually inspect the metal circular part (the back side of the home button) to see if there's any signs of liquid damage
    1. If so, then there's corrosion inside causing the sensor not to function properly. It's not practical to fix, as it requires you to crack open the metal shell, which is not an easy process.
iPhone doesn't always charge when plugged in and stops charging when moved. Solution No. 1: Clean the charging port of any debris/dust in the port.

Solution No. 2: The charge port is damaged.

Home button makes "farting" sound. Check the haptic engine and tighten screws. If the issue is not resolved, replace the haptic engine. ''Sometime the haptic engine need to be reprogram after a screen replacement'' you can reprogram it with a lots of tools like the QianLi LCD Screen True Tone/Vibration/Touch/Battery or the JC V1S. Those tools also work for true tone and activating battery.
No power / 0 amp pulled from the charger / battery fake charging. charging, then a common fault is charger damage to tigris ic
PMIC heats up, no power, full short after power button press PP3V0_NAND is probably shorted, dig out the capacitors around the nand and check for damages.
Random crashing Bad battery / corrupted nand / small shorts
Caps on PP_GPU_VAR / PP_CPU_VAR / PP0V9_SOC_FIXED get really hot with thermal camera Possibly normal, possibly short within the SDRAM or connection between CPU and SDRAM due to improper hot air at top shield removal.
Short on PP_VDD_MAIN Shorted capacitor or electrical damage to a chip where VDD_MAIN is connected to ground WITHIN the chip, or water damage under a chip or within layers of the board where VDD_MAIN is connected to ground.
Missing power lines PMIC is rarely a fault in iPhone 8 unless there is a crack in the chip. More likely you have a data problem that is not telling the PMIC to make those lines
Rear camera black image / bootloop when connected Check the flex cable for damage, then check the camera power line components, as they are frequently corroded.

If there is no SN, check voltages of camera connector - remove rear camera, keep front camera connected and open camera app. If there are voltages missing, replace U3700. Otherwise check I2C lines at pins 18 and 20 of J3900 connector.

If camera SN is readable, but there is only black screen in camera app - check for lose capacitors above the J3900 connector. Since the reading on connector is OL, it's easy to miss non connected components.

Battery stuck on 1%, 3 Min Reboot loop due to battery thermal sensor Connector damage, or transistors used to report the battery percentage got knocked off the board, they're next to the display flex cable, so it's a common repair mistake. Diode mode in the connector to be sure the line is open before replacing the components (Q3200 & Q3201)
40mA short Brain dead phone, likely CPU is not receiving power or has suffered flexion damage
Battery stuck to 1% to 10% and do not seem to charged,

After water damaged.

The battery controller is damaged, replace the battery
iPhone 8 Plus earpiece speaker not working or buzzing after screen replacement. Solution No. 1: Try reseat the cable as the speaker may not be connecting properly to the flex cable. Try reseat the cable to the motherboard as this may also cause it to not work.

Solution No. 2: There is a small piece of black insulation tape that needs to be moved with the Front Camera & Proximity Sensor flex cable. Try using Kapton tape or replacing it with another Front Camera & Proximity Sensor Flex cable.

Solution No. 3: The Front Camera & Proximity Sensor flex cable has been bent or damaged, replace with new cable.

Vibration / WIFI / Audio not working Replace Audio IC

FPC Connectors diode mode readings[edit | edit source]

Use these diode mode maps as a guide to troubleshoot a problem. You must use the RED PROBE on ground and the BLACK PROBE on the pin you are measuring.

For example: you are troubleshooting a no backlight situation, so you probe the pins on the display FPC that correspond to backlight. If a pin says you should read 0.65 and you are reading OL or a short to GND then that's where you need to go.

If instead of getting 0.65 you read 0.58, move on to the next one, remember every multimeter is different and even slight differences in temperature affect this readings. What you are looking for is extreme differences in values, if you are expecting some value and you get a short to ground that is where it is more likely to be your issue.

iPhone 8[edit | edit source]

Display and Touch connector (J) & TouchID Home Button connector (J)[edit | edit source]
Diode mode for iPhone 8 Display/Touch connector. Bottom left goes towards coaxial antennae.
iPhone 8 TouchID charge port connector. Bottom left goes to the lower antennae
Charge port / dockflex Connector (J)[edit | edit source]
iPhone 8 DockFlex charge port connector. Top goes towards the SIM card reader.
Battery connector (J)[edit | edit source]

(No original data as of yet, please refer to 8 Plus which should be pretty much the same)

iPhone battery connector. Bottom left goes to the edge of the board, next to the bottom of the battery.

Rear camera Connector (J)[edit | edit source]
iPhone 8 rear camera connector. Top right goes to the top right of the board, under the rear camera.
Front camera, proximity sensor, earspeaker, ambient light sensor connector (J)[edit | edit source]
iPhone 8 front flex connector. Contains front camera, proximity sensor, ambient light sensor, earspeaker. Top right goes to top of the board, under the rear camera.
Volume and Power buttons, flashlight, ringer switch (J)[edit | edit source]
iPhone 8 Volume, power buttons, ringer switch and flaslight connector. Top left goes to top edge of the board, next to the mute/ringer switch.

iPhone 8 Plus[edit | edit source]

Display and Touch connector (J5700) & TouchID Home Button connector (J5800)[edit | edit source]
Diode mode for iPhone 8 Plus Display/Touch and TouchID/Home Button connector. Pin 1 goes towards SIM card reader.
Charge port / dockflex Connector (J6400)[edit | edit source]
iPhone 8 Plus DockFlex charge port connector. Pin 1 goes to the top left, towards the SIM card reader.
Battery connector (J3200)[edit | edit source]
iPhone 8 Plus battery connector. Bottom left goes to the edge of the board, next to the bottom of the battery.
Rear cameras Connectors (J4000 left cam & J3900 right cam)[edit | edit source]
iPhone 8 Plus rear cameras connectors. Pin 1 goes to the top right of the board, under the rear cameras.
iPhone 8 Plus rear cameras connectors. Pin 1 goes to the top right of the board, under the rear cameras.
Front camera, proximity sensor, earspeaker, ambient light sensor connector (J4200)[edit | edit source]
iPhone 8 Plus front flex connector. Contains front camera, proximity sensor, ambient light sensor, earspeaker. Pin 1 goes to top right, top of the board, under the rear camera.
Volume and Power buttons, flashlight, ringer switch (J4300)[edit | edit source]
iPhone 8 Plus Volume, power buttons, ringer switch and flaslight connector. Top left goes to top edge of the board, next to the mute/ringer switch.

BaseBand PMU diode mode readings[edit | edit source]

iPhone 8 INTEL BB PMU Diode mode readings. Pin 1 points to Top Left