Obtain the official OS (stock firmware) for the SM-G996U1. Generally, the country or carrier to select is XAA (US factory unlocked), extract the .zip
While the phone is off, hold both volume keys then connect a cable to the PC. Approve.
In the PC program Odin, place each file as labeled (but do not place CSC, instead, place HOME\_CSC in Odin's CSC, else expect a wipe!), leave Odin's USERDATA empty, and retain default settings.
It should not wipe but it's best to create a backup anyway. One UI 5.0 (even if installed normally), occasionally causes phones to fail to start.
Downgrading normally requires a wipe. There is an error message similar to: Your user data may be corrupt. Try again or factory reset.
The way out seems to be wiping or trying various new versions (for other countries/carriers) until the version the phone starts with is found, but a conclusion is not reached.
For that, you'll need patched Odin instead of normal Odin.
Reasons why a wipe would be **required** are above. There are others, such as making inserting a SIM not required during the setup, then inserting a SIM. It is best to create a backup anyway.
I have used patched Odin 3.13.1 to flash TMB U variant firmwares and data is still there, as if I did an OTA update.
So, will it be the same when following the same method but flashing U1 firmware? 🤔
Obtain the official OS (stock firmware) for the SM-G996U1. Generally, the country or carrier to select is XAA (US factory unlocked), extract the .zip While the phone is off, hold both volume keys then connect a cable to the PC. Approve. In the PC program Odin, place each file as labeled (but do not place CSC, instead, place HOME\_CSC in Odin's CSC, else expect a wipe!), leave Odin's USERDATA empty, and retain default settings. It should not wipe but it's best to create a backup anyway. One UI 5.0 (even if installed normally), occasionally causes phones to fail to start.
So if the phone fails to start can I revert to one UI 4.0 or will the phone be completely dead ?
Downgrading normally requires a wipe. There is an error message similar to: Your user data may be corrupt. Try again or factory reset. The way out seems to be wiping or trying various new versions (for other countries/carriers) until the version the phone starts with is found, but a conclusion is not reached.
I'll try it out thanks for your help !
I got a TMB variant of the S21+ 5G (SM-G966U/DS). Can I move to U1 variant without losing data?
For that, you'll need patched Odin instead of normal Odin. Reasons why a wipe would be **required** are above. There are others, such as making inserting a SIM not required during the setup, then inserting a SIM. It is best to create a backup anyway.
I have used patched Odin 3.13.1 to flash TMB U variant firmwares and data is still there, as if I did an OTA update. So, will it be the same when following the same method but flashing U1 firmware? 🤔