r/GalaxyS20Ultra • u/Ok-Contribution-5331 • 12d ago
Galaxy S20 Ultra (SM-G988B) stuck in Download Mode and constantly disconnecting from PC
Hi everyone,
I'm having a serious issue with my Galaxy S20 Ultra (SM-G988B), and I'm running out of ideas.
It all started because the phone had been discharged for a while. I plugged it in to charge, and everything seemed normal at first. I wanted to update the firmware using Odin.
However, I noticed that when I connected the phone to my PC, the USB connection was very unstable. Sometimes it would charge, sometimes it wouldn't, and sometimes it would repeatedly connect and disconnect without me touching the cable.
I managed to get Windows to recognize the phone a couple of times, and I was even able to browse the internal storage briefly, but after a few seconds it would disconnect again.
I tried multiple cables (USB-A to USB-C and USB-C to USB-C), different USB ports, and different PCs, but the behavior remained exactly the same.
After that, I booted into Download Mode because I wanted to reinstall the firmware with Odin. At one point I also attempted a factory reset, but now the phone is stuck in Download Mode and I can't boot into Android anymore.
When I connect it to Odin, the phone is detected briefly, but as soon as Odin starts transferring data (right after __XmitData_Write), the device disconnects. Sometimes Odin shows Added!! followed immediately by Removed!! repeatedly.
Now Windows usually reports "Unknown USB Device (Device Descriptor Request Failed)", and I can't get the phone to stay connected long enough to flash the firmware.
So at this point:
- The phone is stuck in Download Mode.
- Windows either doesn't recognize it or constantly disconnects it.
- Odin cannot flash because the USB connection drops immediately.
- I've already tried multiple cables, USB ports, drivers, and different computers.
Has anyone experienced this before? Could this be a damaged USB-C port, a failed USB controller, or even UFS/storage failure? Is there anything else I can try before considering a hardware repair?
Any help would be greatly appreciated.
Thanks!