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| Diagnosing iPhone “No IMEI / No Service” via RFFE Bus Analysis with ESP32 | |
|---|---|
| Device | iPhone X, iPhone XS, iPhone XS Max, iPhone 11, iPhone 11 Pro, iPhone 11 Pro Max, iPhone 12, iPhone 12 Mini, iPhone 12 Pro, iPhone 12 Pro Max, iPhone 13, iPhone 13 Mini, iPhone 13 Pro, iPhone 13 Pro Max, iPhone 14, iPhone 14 Plus, iPhone 14 Pro, iPhone 14 Pro Max, iPhone 15, iPhone 15 Plus, iPhone 15 Pro, iPhone 15 Pro Max |
| Affects part(s) | Main Logic Board |
| Needs equipment | ESP32 Development board, flux, jumper wires, microscope, soldering iron |
| Difficulty | ◉◉◉◌ Hard |
| Type | Soldering |
Problem description
You’re working on a phone (e.g. iPhone 12/13/14/15) that powers on normally, but when you go to the dialer and type *#06#, no IMEI is shown. Baseband-related functions are not working (no signal, no cellular data).
Traditional board-level repairs (Baseband CPU reballing, BBPMU replacement) may not solve it — because the issue lies deeper: RFFE communication failure.
Symptoms
- Dialing *#06# shows no IMEI or blank screen
- Phone shows “No Service” even with a working SIM
- Restores successfully via iTunes/3uTools but IMEI is still missing
- Logic board shows no physical damage or shorts on power lines
Diagnostic steps
- Initial Checks:
- Confirm "No Service" by inserting a working SIM
- Dial *#06# and check if IMEI appears
- Perform restore via 3uTools — see if "No Service" still showing after restore
- Visual Inspection:
- Inspect for prior work (especially RF interposer swaps)
- Check for water damage near the RF section and PA modules
- Inspect shielded areas and sandwich joints
Repair Steps
Step 1: Flash Firmware to ESP32
- Connect the ESP32 board to your PC via USB.
- Open flash_download_tool_3.9.3.
- Select the appropriate .iso files from the “ISO Files” folder.
- Hit START to begin flashing the ESP32.
- Once complete, the ESP32 is ready to use as a scanner.
Step 2: Connect Jumper Wires to Logic Board
Take an iPhone 12 logic board as an example:
ESP32 Pinout to Logic Board Mapping:
- D22 → SCL on iPhone
- D21 → SDA on iPhone
- GND → Ground
- 3V3 → 1.8V line on logic board
Use the appropriate RFFE test point maps from the “Test Points / RFFE Maps” folder for your specific model.
Note: iPhone 12 / 12 Pro has 8 separate RFFE buses.
Solder the jumper wires to the correct test points for:
- SDA
- SCL
- 1.8V
- GND
Step 3: Scan for Non-Responding PAs
- Open the RFFE Scanner software on your PC.
- Select the correct COM port (corresponding to ESP32).
- Click Scan.
The software will begin scanning the PA modules on the connected bus.
- A sample output:
{"0X3": 0}
This means PA address 0x3 is not responding.
- In contrast:
{"0X3": 1}
means the PA is responding normally.
Repeat this scan for each RFFE bus by changing the soldered points as per your map.
Step 4: Fix the Non-Responding PA
- Most commonly, the issue is a faulty PA module, which must be replaced.
- In some cases, the problem lies in the interposer (sandwich) layer, where a signal line may be broken or disconnected.
- Visual inspection and continuity testing between the CPU, interposer, and PA are recommended.