Failed -remote 39-flashing Lock Flag Is Locked. Please Unlock It First 39-- -

This error message indicates that you are trying to write or "flash" software to a partition while your device's bootloader is still locked. In most Android-based devices, the bootloader must be explicitly unlocked before it will allow any manual changes to the system files. Phase 1: Enable OEM Unlocking

Before you can run a terminal command to unlock the device, you must give the device permission from within the settings menu.

Enable Developer Options: Go to Settings > About Phone and tap on Build Number seven times until it says "You are now a developer."

Toggle OEM Unlocking: Go to Settings > System > Developer options and switch on OEM unlocking.

Enable USB Debugging: While in Developer options, ensure USB debugging is also turned on. Phase 2: Run Unlock Commands

Once the software toggle is active, you must use a computer with Android Platform Tools installed to finalize the unlock.

Enter Fastboot Mode: Connect your device to the computer and run:adb reboot bootloader

Standard Unlock: Try the modern standard command first:fastboot flashing unlock This error message indicates that you are trying

Legacy/OEM Unlock: If that fails, some older or specific devices use:fastboot oem unlock

Critical Partition Unlock: If you are trying to flash low-level files like the bootloader itself, you may also need to run:fastboot flashing unlock_critical Important Troubleshooting

Lock and unlock the bootloader | Android Open Source Project

The error FAILED (remote: 'Flashing Lock Flag is locked. Please unlock it first!') occurs when you attempt to flash firmware or partitions to an Android device while the bootloader is in a "LOCKED" state. On many modern devices, simply enabling "OEM Unlocking" in settings is not enough; you must also execute a specific hardware-level unlock command while in fastboot mode. Error Analysis

Cause: The device security flag is preventing any modification to the system partitions. This is a safety feature to prevent unauthorized software (like malware or unverified firmware) from being installed.

State: You are likely in fastboot mode or fastbootd, where the device is waiting for commands but rejecting those that write data because the "lock flag" is active. How to Install Ubuntu Touch on the Jingpad A1/C1

failed -remote 39-flashing lock flag is locked. please unlock it first How to Fix It You must remove the

3. How to fix it

Step 1 – Check all external covers
Open and firmly close every door/cover on the device (front, side, rear, top scanner unit if copier). Listen for clicks.

Step 2 – Look for a physical lock lever
Some large copiers have a transport lock for the drum/fuser unit. Unlock it if present.

Step 3 – Power cycle the device
Turn off, wait 30 seconds, turn back on. The flag sensor may reset.

Step 4 – Check for jams
Remove paper trays, look for stuck paper behind the fuser or near duplexer. Even a small scrap can hold a lock flag.

Step 5 – Reseat toner/fuser/drum
Remove and reinstall each removable unit. A misseated unit keeps the lock flag active.

Step 6 – Manual flag reset (advanced)
If you’re technical and the device is off, locate the interlock flag (plastic tab near microswitch). Gently move it to see if it springs back. If broken, needs service.

How to Fix It

You must remove the write protection before attempting to flash again. Here are the standard steps to do this: trying to install a custom ROM

  1. Send an Unlock Command:

    • If you are using a command-line tool (like stm32prog, openocd, or a vendor-specific CLI), look for an erase or unlock flag.
    • Example: stm32prog -u or openocd -c "stm32f1x unlock 0".

  2. Use a "Mass Erase":

    • Many devices will not let you unlock specific sectors individually. You may need to perform a Mass Erase of the flash memory to clear the lock flag. This will delete all existing firmware on the device.

  3. Check for Physical Jumpers/Pins:

    • If this is an embedded board, check if the BOOT0 pin or a physical "Write Protect" jumper is set. You may need to move a jumper to position 0 or 1 to enter a mode that allows unlocking.

  4. Power Cycle:

    • After sending the unlock command, you often need to power cycle the device (turn it off and on) or reset it for the new unlocked state to take effect.

Possible Causes

  1. Hardware security fuse set (e.g., OTP or e-fuse) preventing write access.
  2. Bootloader-enforced write-protection (locked via software flag).
  3. Device in production/programming lock mode (requiring an authentication/unlock sequence).
  4. Incorrect flashing tool or protocol version causing misinterpretation of lock state.
  5. Corrupted flash metadata making lock flag appear set.
  6. Insufficient privileges or missing unlock command in flashing sequence.
  7. Cable/connection issues causing partial communications and false lock detection.

Root Cause Analysis (example scenarios)

  • Scenario A: OTP fuse set during secure provisioning — permanent lock requiring chip replacement or vendor support.
  • Scenario B: Bootloader lock bit set but reversible — requires authenticated unlock sequence or debug unlock command.
  • Scenario C: Tool mismatch — flashing tool misreads status; newer tool or firmware will resolve.

6.3 Check for Conflicting Flash Modes

  • Ensure you are not in SLOT A or SLOT B mismatch (A/B partitioning). Switch slots: 
    fastboot set_active other
fastboot reboot bootloader

Introduction

Few things are more frustrating in the world of embedded systems, Android development, or firmware flashing than encountering a cryptic error message right in the middle of a critical operation. One such notorious message is:

failed -remote 39-flashing lock flag is locked. please unlock it first

If you are seeing this error pop up in your command-line interface—whether you are using fastboot, trying to install a custom ROM, or unbricking a device—you have come to the right place.

This long-form article will dissect every component of this error, explain why it occurs, and provide step-by-step solutions to unlock the "lock flag" and successfully flash your device.

Abstract

A concise report describing the occurrence, root causes, diagnostic steps, and recommended remediation for the error message: "failed -remote 39 - flashing lock flag is locked. please unlock it first 39--".