| Cause | Explanation | |-------|-------------| | Door / cover open | A toner access door, paper jam release cover, or front cover is slightly open. | | Interlock flag stuck | A small plastic flag that presses a microswitch is broken or stuck in locked position. | | Paper jam | Device locks all moving parts; flag stays locked until jam cleared. | | Fuser or drum unit not fully seated | Removable units have lock flags that must click into place. |
Reboot to bootloader:
Before diving into unlock methods, ensure the following:
These devices require the proprietary . You must link your Mi Account to the device in Developer Options and often wait a mandatory period (usually 168 hours) before software allows the unlock.
This security feature is not an attempt to frustrate developers; it protects you and the device. The primary reasons for this lock include: | Cause | Explanation | |-------|-------------| | Door
The error is a protective security message triggered by Android’s Android Open Source Project Bootloader Protection when a user attempts to modify firmware partitions via fastboot while the bootloader remains securely locked. Turning on "OEM Unlocking" inside your phone's Android Developer Options menu only authorizes the device to receive unlock protocols; you must still execute explicit command-line instructions within a fastboot window to successfully change the system's lock state.
Manufacturers sometimes lock the flashing flag tighter in newer updates. Flash an older stock ROM (if allowed) first, then unlock.
This is the core of the problem. Modern devices include a —a security mechanism that prevents unauthorized writing to critical partitions (like boot , recovery , system , or vbmeta ). When this flag is locked , the bootloader rejects any fastboot flash commands.
The "Failed -Remote 39:Flashing Lock Flag is Locked. Please Unlock it First" error, while frustrating, is a protective measure designed to prevent unauthorized modifications to a device's firmware. By understanding the causes and following the appropriate steps to resolve the issue, users and technicians can successfully overcome this hurdle. Always proceed with caution and ensure you have backups of critical data before attempting any firmware modifications. | | Fuser or drum unit not fully
This error typically occurs when you're trying to flash a system image or custom recovery via , but your device's bootloader
: These often require a unique "Unlock Code" obtained from the manufacturer's website.
Refers to a failure code within the debugger interface, often associated with command timeouts or rejected write commands.
If you cannot unlock the bootloader (e.g., restricted carrier models like Verizon), you cannot flash custom partitions. This security measure cannot be bypassed easily. This security feature is not an attempt to
Back up all your data, as the process will wipe your device clean. Then, enable Developer Options and toggle on OEM Unlocking and USB Debugging as described earlier.
Because different manufacturers utilize custom Fastboot arguments, execute the following commands in sequence until the device screen prompts you to confirm a system wipe: fastboot flashing unlock Use code with caution. Legacy device command variations: fastboot oem unlock Use code with caution. or fastboot oem unlock-go Use code with caution.
If the unlocked variable returns as no or false , your device's bootloader is definitely locked. If it returns yes but you are still getting the error, proceed to the advanced steps below.