Fix Baseband Unknown / No IMEI After Flashing
Your phone shows "Unknown" baseband and network doesn't work? This is scary but almost always fixable.
Understanding the Problem
What is Baseband?
Baseband (also called modem firmware) is software that controls:
- Cellular connectivity
- IMEI storage
- Network registration
- Signal management
When baseband shows "Unknown":
- No cellular network
- No calls or texts
- Mobile data doesn't work
- IMEI may show as null
Check Your Status
Settings → About Phone
- Baseband version: Should show version number
- IMEI: Should show 15-digit number
If either shows "Unknown" or blank = problem
Common Causes
| Cause | Likelihood | Fix Difficulty |
|---|---|---|
| Wrong firmware flashed | Very High | Easy |
| Incomplete flash | High | Medium |
| EFS partition corruption | Medium | Medium-Advanced |
| Hardware issue | Rare | Repair needed |
Fix 1: Flash Correct Firmware/Modem
Most common cause and fix.
The Problem
You flashed a ROM that needs different firmware, or skipped firmware flash.
The Solution
- Find firmware version required by your ROM
- Flash the modem/baseband from that firmware
For Xiaomi/Redmi/POCO
1. Download correct firmware from XiaomiFirmwareUpdater
2. Boot to TWRP
3. Install → Select firmware.zip
4. Reboot
5. Check baseband version
For Samsung
1. Download correct firmware from SamMobile
2. Extract CP_xxxx.tar (this is modem)
3. Boot to Download Mode
4. Flash only CP in Odin
5. Reboot
For Other Brands
Flash the modem partition from matching stock firmware:
fastboot flash modem modem.img
# OR
fastboot flash radio radio.img
Names vary by device (modem, radio, NON-HLOS).
Fix 2: Reflash ROM with Firmware
Do a complete clean flash with firmware:
1. Boot to TWRP
2. Wipe:
- System
- Vendor
- Cache
- Dalvik
- Data (if needed)
3. Flash firmware FIRST
4. Flash ROM
5. Flash GApps (if needed)
6. Reboot
Order matters! Firmware before ROM.
Fix 3: Fix IMEI Without Baseband Issue
If baseband shows correctly but IMEI is wrong/missing:
Check EFS Backup
If you have EFS backup from before the issue:
TWRP → Restore → Select EFS backup
Reboot
IMEI Repair (Complex)
For devices with corrupted IMEI storage:
Method varies by chipset:
Qualcomm devices:
- May need QPST/QFIL tools
- Requires knowledge of DIAG mode
- Device-specific process
MediaTek devices:
- SP Flash Tool can sometimes help
- Need scatter file for device
Samsung:
- Can sometimes restore via Download Mode tools
- Service centers have official tools
⚠️ Warning: IMEI modification may be illegal in some countries. Only restore YOUR own valid IMEI.
Fix 4: ADB Modem Reset
Sometimes simply resetting modem helps:
adb shell
su
echo -e "AT+CFUN=0" > /dev/smd0
sleep 5
echo -e "AT+CFUN=1" > /dev/smd0
exit
Or via Settings:
Settings → Network → Mobile Network
Toggle Airplane Mode on/off
Force restart device
Fix 5: Restore EFS Partition
EFS (Encrypted File System) stores IMEI and other unique data.
If You Have EFS Backup
1. Boot to TWRP
2. Go to Restore
3. Select your EFS backup
4. Restore only EFS partition
5. Reboot
If You Don't Have Backup
Without EFS backup, options are limited:
- Service center can sometimes recover/reprogram
- Some devices have IMEI in other partitions
- Rooted apps can sometimes write to IMEI
Prevention: Backup EFS
Before any major modifications, backup EFS!
Via TWRP
1. Boot to TWRP
2. Backup → Select only EFS
3. Name backup clearly (e.g., EFS_working)
4. Store in safe location (not just phone)
Via ADB
# Backup EFS (paths vary by device)
adb shell
su
dd if=/dev/block/by-name/efs of=/sdcard/efs_backup.img
exit
adb pull /sdcard/efs_backup.img
Device-Specific Solutions
Xiaomi
1. Check firmware version needed by ROM
2. Download from xiaomifirmwareupdater.com
3. Flash via TWRP before ROM
Common issue: Different regional variants need different firmware.
Samsung
1. Download full firmware from SamMobile
2. Flash complete package OR just CP
3. Modem is in CP_xxxx.tar
Exynos and Snapdragon have different modems!
OnePlus
1. Oxygen OS firmware needed for most ROMs
2. Flash OOS firmware ZIP before custom ROM
3. Or use OOS modem extracted as flashable ZIP
Pixel
1. Download factory image from Google
2. Extract radio.img
3. Flash: fastboot flash radio radio.img
When Nothing Works
Signs of Deeper Issues
- Baseband shows "Unknown" on stock ROM too
- Multiple firmwares don't fix it
- IMEI disappeared even on stock
Possible Hardware Issues
- Modem chip damaged
- Antenna connection loose
- Board-level failure
Solutions
- Service Center: They have diagnostic tools
- Professional Repair: Third-party mobile repair
- Box Tools: SP Flash Tool, Miracle Box, etc. (need expertise)
IMEI Null vs Baseband Unknown
Different but related issues:
IMEI Null/Invalid
- IMEI storage corrupted
- EFS partition issue
- Can sometimes be restored
Baseband Unknown
- Modem firmware not loaded
- Usually firmware mismatch
- Flashing correct firmware fixes it
You might have both, or just one.
Testing Fix Success
After applying fixes:
1. Reboot device
2. Settings → About Phone
3. Verify baseband shows version number
4. Verify IMEI shows 15-digit number
5. Insert SIM card
6. Check network registration
7. Make test call
8. Test mobile data
Checklist
Baseband Unknown Fix Checklist:
[ ] Identify what firmware your ROM needs
[ ] Download matching firmware
[ ] Flash firmware (before ROM if reflashing)
[ ] Reboot and check baseband
[ ] If still unknown, try full stock flash
[ ] If IMEI also missing, check EFS
[ ] Restore EFS backup if available
[ ] As last resort, seek professional help
Baseband issues are scary because they affect core phone functionality. But in 90%+ of cases, it's simply a firmware mismatch. Match your firmware to your ROM, and you'll be back in business.
Keywords: baseband unknown fix, imei missing android, modem fix custom rom, no network after flash, fix baseband version