FP4 stays black after reboot

Help Fairphone 4
,
1

I have a FP4 with stock android (256GB edition), 3 years and 4 months old (still first battery). I have Android 15, I got a system update at the start of this year (Telekom germany user) which I installed and rebooted successfully. Due to the phone not booting right now, I cannot say which update exactly.

Yesterday it felt like the battery was draining fast (from 35 to 30% in 20 minutes), so I rebooted to maybe kill some app running wild (except emergency service apps there shouldn’t be much stuff in the background). This was the last thing it did. Everything was working before the reboot, system, apps, screen, microphones, loudspeaker, cameras, buttons, touch, fingerprint sensors. No erroneous behaviour noticed by me. I cannot say how full the filesystem is, I checked some months ago and not even 128GB were used - so it is extremely likely, that the filesystem is not full.

Symptoms:

  • Phone seems completely dead
  • Screen stays black
  • No vibration when trying to switch it on
  • No sound whatsoever

List of things I tried to get it working:

  • searched the forums for related blackscreen problems without success
  • removed and reinserted the battery
  • removed the battery overnight for any capacitors or internal batteries to discharge
  • pressed the power button 20 seconds, 5 times in a row, random patterns
  • connected the phone to different chargers and charger cables
  • inserted my replacement battery, connecting it to a charger for over an hour
  • removed the SIM card and tried to boot, reinserted the SIM card
  • disassembled and reassembled my phone strictly following the official FAIRPHONE 4 HOWTO videos on YouTube, using my iFixit tools, wearing an ESD protector - as suggested by the support instructions to fix potential problems. Some minor cleaning on the way, all btb connectors were in place and are again
  • Phone wasn’t wet beforehand, no old or current water ingress visible when disassembling it, left the back plane open overnight for any theoretical moisture to dissipate in a heated room (~20°C, ~40% RH)

The only curious thing is:

  • When connecting the phone to my Windows 11 PC, there’s the “device connected” sound (low note, high note). Then a disconnect sound (high note, low note) follows repeatedly every roughly 10 seconds
  • Devicemanager shows “other devices” → “QUSB_BULK_SN:someid” with a yellow exclamation mark.
  • I tried to install the Google USB driver, device manager claiming it’s not the proper driver. I used Windows update to install missing drivers - without success
  • I installed the Google platform tools. adb devices says it found nothing.

Next step would be to connect the phone to a Linux computer which I currently don’t have at hand. Anyway, I did unlock the developer options, but not adb debugging, when the phone was still running, so I don’t expect much from adb. (I haven’t had any adb experience yet, but as technical personell I’m learning fast)

I never rooted the phone and generally using standard apps from Playstore and F-Droid. I did unlock the developer options, but never fiddeled around there, especially not recently.

Any ideas how to proceed further?

Software Update: FP4.QREL.15.15.2
2

See Software Update: FP4.QREL.15.15.2 - #190 by cdiddy987 . This is a borked (and already recalled) update. You were just unlucky to install it in the few days it was available. There’s no easy way for self-repair. Contact support to get a replacement phone. They should be relatively quick in this matter.

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3

Thanks for the advice, I’ll check it out.

I guess all my data on the phone is lost? (so the support cannot rescue/transfer anything?)

4

But that was last year December 22nd and not this year. So I don’t think that’s the reason for the black screen here.
And it didn’t brick all phones, mine still works even after another reboot.

5

But that was last year December 22nd and not this year.

Is update distribution bound to Fairphone or to my provider? (Telekom Germany)

Anyway, the update number looks somewhat familiar to me, though this is not proof. I recall it had November 2025 patch level.

6

To both, but as Fairphone recalled the update, I don’t think you can get it now via Telekom.

7

The more I think about it, the more likely it becomes to me, that installation was earlier than the start of this year. Hard to say. I’ve almost read complete FP4.QREL.15.15.2 thread and all the symptoms seem to apply to me. I’ve reached out for the support.

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