Samsung S21 Ultra 5G Sudden Blackout & Unlocking Issues

[WsM]

Samsung S21 Ultra 5G Sudden Blackout & Unlocking Issues

I’ve been using my Samsung S21 Ultra 5G since I bought it brand new, and it has been working fine until today. Suddenly, the phone is acting abnormally without any prior warning.

Issues Faced:

Sudden Blackout/Shut Down: The phone turns off randomly without any warning, and the display goes completely dead.

Not Charging: When the phone is off, it doesn’t respond to charging. (Rarely it does work)

Forced Restart Required: The only way to turn it back on is through a forced restart.

Biometric Failures: Fingerprint scanner gives a 'Fingerprint corrupted' error, and face recognition does not work. (Not always but sometimes)

Unlocking Issue: After a force restart, the phone sometimes accepts the pattern but locks back immediately. (Not always but sometimes)

Cache Partition Cleared, but No Improvement: I tried clearing the cache partition, but the issue persists.

Safe Mode: Tried as well but no improvements.

When the phone is turned on and unlocked, it works normally, as long as the display is on & phone is busy with somethinglike watching a video or browsing, but I can’t be sure for how long before another sudden shutdown.

Has anyone experienced similar issues? What could be causing this, and is there a way to fix it? Any advice would be greatly appreciated.

TIA

[Zayyar2312]

I think you might go to the service centre your issue are really bad

[TraverS]

Motherboard probably 😮. But service center will help.

[ajuneeisnig]

Hey ajuneeisnig here
It sounds like your Samsung S21 Ultra 5G is experiencing a mix of hardware and software-related failures. Here are some possible causes and troubleshooting steps:

Possible Causes:

1. Battery or Power Management Issue – Sudden shutdowns and unresponsiveness to charging suggest a failing battery or power IC.


2. Corrupt System Files – The biometric failures and random lockouts may indicate corrupted firmware.


3. Overheating or Hardware Fault – A failing component (e.g., motherboard, display IC) could be causing blackouts.


4. Software Bug – A recent update or rogue app might be triggering the problem.



Troubleshooting Steps:

1. Check Battery & Charging

Try a different charger and cable (preferably Samsung’s original 25W or 45W charger).

Plug the phone in for 30 minutes and force restart (Press & Hold Power + Volume Down for 10+ seconds).


2. Boot into Safe Mode Again

If you haven’t already, boot into Safe Mode by holding Power > Long-Press on "Power Off" > Select Safe Mode.

If it works fine in Safe Mode, a third-party app is likely causing the problem. Uninstall recent apps.


3. Test in Recovery Mode

Power Off the phone.

Press & Hold Volume Up + Power until the Samsung logo appears.

If you see the Android Recovery menu, the screen/display is fine.

Try "Wipe Cache Partition" (which you’ve done) or "Repair Apps."


4. Check Battery Health

Dial *#0228# or install the Samsung Members app > Go to Diagnostics and check battery health.


5. Reinstall Firmware (Potential Fix for Corrupt System)

If the issue persists, a clean firmware reinstall may help:

Back up your data using Smart Switch.

Use Samsung Smart Switch on a PC to reinstall the latest firmware.

Alternatively, Odin software + stock ROM (advanced users only).


6. Hardware Check & Repair

If all else fails:

Visit Samsung Support or a service center for a hardware diagnosis.

The motherboard or battery may need replacing.


Final Thoughts

Since your phone is unresponsive to charging and only works when active, it’s likely a battery, power IC, or motherboard issue. If software fixes don’t work, Samsung Service is your best bet.

[ajuneeisnig]

If this helps please mark me as an accepted solution

[Samsung_specialist]

We apology for this issue that you are facing , could you try these steps:

Check for possible causes of unexpected phone shutdowns.
Disable Auto-restart on the phone.
Reboot the phone or tablet in safe mode.
Perform a factory data reset on your phone or tablet.
for more details :https://www.samsung.com/ae/support/mobile-devices/samsung-phone-unexpectedly-powers-off/#:~:text=Che....

If the problem persists after following these steps you need to visit the nearest service center : https://www.samsung.com/ae/support/service-center/