Bootloader unlock failed

Sony Xperia 10 III (Dual-Sim), SFOS

I reflashed the smartphone and wanted to close the bootloader. After I closed the bootloader via fastboot (with “fastboot oem lock”), I was able to start the device exactly once. After that, I received a system message that the system was corrupt and the device switched off again automatically after five seconds. This means that I no longer have any access to the smartphone.

Afterwards I tried to flash the smartphone again. Unfortunately, I didn’t write down the IMEI. However, I discovered that there are several numbers printed on the SIM card compartment that could be the IMEI.

So I started fastboot again and received a response via “fastboot devices” in the form “XX615X2X4X fastboot”. The smartphone is obviously recognised. However, if I now enter “fastboot oem unlock” and the assumed IMEI (15 digits), I get the error message “FAILED (remote: ‘Incorrect format for unlock data’)”.

What am I doing wrong? Does anyone know a way of finding out the IMEI or verifying the assumed one? What does the format look like? Or is there another way (with Linux) to get access to the bootloader/ the smartphone?

You don’t use the IMEI to unlock the phone. You need an unlock code.

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But according to Sony I do need the IMEI to get the unlock code … And I don’t have any access to the smartphone

The IMEI can be found on the SIM holder.

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If you still have the original packaging, usually there is IMEI printed on the box.

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That would be good, but unfortunately I no longer have a box. It’s also stupid that I can’t get any further on the Sony website (Unlock bootloader | Developer World). I haven’t yet been able to work out why I wasn’t redirected when I selected the right smartphone and accepted the two click boxes below.

Above the two click boxes you also have to enter your IMEI, which you find on the sim holder (very small characters)

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OR you could open the phone dialler app and enter



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Embarrassing, embarrassing! I thought the input field was a heading. Bootloader is open and the new system is installed. Many thanks to everyone for their help.

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