Samsung Galaxy M31 users commonly run into IMEI showing as null or Baseband unknown, especially after using an unofficial or third-party flashing tool. The Stock ROM below is a direct fix for this. This build is made specifically for the Exynos 9611 chipset, so confirm your exact model number (e.g. SM-M315F) before downloading.
Before you download: full firmware flashing via Odin wipes all data, so back everything up first. And always confirm the CSC/region code matches your device — using firmware from the wrong region can lead to problems after flashing.
Links above point to the firmware's official page — the actual file download starts from there. Full firmware files are large, so make sure you have a stable connection before starting.
How to Flash Samsung Galaxy M31 Using Odin
Download the firmware and extract the .zip fully to get the .tar/.tar.md5 file — Odin won't read a zipped folder.
Install Odin and the Samsung USB driver from the links below, then open Odin.
Power off the phone, then hold Volume Down + Volume Up and connect the USB cable to boot into Download Mode. Press Volume Up to confirm.
Connect the phone to your PC using a good-quality USB cable — cheap cables are a common cause of connection drops mid-flash.
In Odin, click "BL", "AP", "CP", and "CSC" and select the matching files extracted from the firmware package.
Once the port shows as connected (blue/green "COM" box), hit "Start" and let it run — don't disconnect the phone during this step.
The phone will reboot on its own once flashing finishes. First boot can take a few minutes longer than usual, so give it time.
Common Flashing Errors and How to Fix Them
"FAIL!" in Odin — usually a wrong CSC/region combination or a corrupted file. Re-download the firmware and confirm the CSC code matches your device.
Phone not detected in Odin — almost always a driver issue. Install the Samsung USB driver from the link below, then re-enter Download Mode and try again.
Stuck at "SW REV CHECK FAIL" — this means you're trying to downgrade the bootloader/binary version, which Samsung blocks by default. Flash a firmware with an equal or higher binary number instead.
Frequently Asked Questions
Is this firmware official? Yes, these are unmodified stock builds.
Will flashing delete my data? A full firmware flash (BL+AP+CP+CSC) wipes the device, so back up anything important first.
My model number doesn't match exactly — can I still use this? Stick to the exact CSC/region code (INS) shown in the table above. Flashing firmware built for a different region can cause network or boot issues.
Tools You'll Need
Make sure Odin and the correct USB driver are already installed on your computer before you begin. More often than not, a flash fails because of a driver problem, not the firmware itself.
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