Unlock Bootloader Lenovo Vibe X3 (X3A40) Guide

Unlocking the bootloader on your Lenovo Vibe X3 (model X3A40) lets you install custom recoveries, flash custom ROMs, and gain full root access. This guide walks you through the official unlock process using Lenovo’s bootloader unlock tool, covering everything from enabling developer options to submitting your device credentials. Before you begin, back up all important data—unlocking wipes your phone completely.

What You’ll Need

A Windows PC (the Lenovo unlock tool only runs on Windows)
USB cable that supports data transfer (not just charging)
Your Lenovo Vibe X3 with at least 70% battery
Backup of all personal data (photos, contacts, files) because unlocking erases everything
A Lenovo account (free to create at lenovo.com)
ADB and Fastboot drivers installed on your PC (Lenovo USB drivers or Google USB driver)
Internet connection on your PC

Step-by-Step

Back up your phone. Connect to a computer or use cloud storage to save photos, contacts, messages, and any other files you want to keep. Unlocking will factory reset the device.
Enable Developer Options. Go to Settings > About Phone and tap Build Number seven times. You’ll see a toast saying “You are now a developer!”
Turn on OEM Unlocking. Go to Settings > Developer Options and toggle OEM Unlocking to ON. If this option is greyed out or missing, your device may already be carrier-locked or not eligible for official unlocking.
Enable USB Debugging. In the same Developer Options menu, toggle USB Debugging to ON.
Install ADB and Fastboot on your PC. Download the platform-tools from the Android developer site and extract them to a folder like C:\adb. Also install the Lenovo USB drivers if Windows doesn’t recognize your phone.
Find your device serial number. On your phone, open the dialer and type *#*#1357946#*#*. A popup will show your serial number (also called SN). Write it down. Alternatively, go to Settings > About Phone > Status to see the serial number.
Find your device IMEI. Dial *#06# and note the IMEI number(s). You’ll need this for the unlock request.
Submit an unlock request on Lenovo’s official site. Visit the Lenovo bootloader unlock page (search “Lenovo bootloader unlock”). Sign in with your Lenovo account, enter your device model (X3A40), serial number, and IMEI, and agree to the terms. Lenovo will send an email with an unlock code (a long alphanumeric string) and a link to download the unlock tool.
Download and run the Lenovo Smart Unlock Tool. Extract the ZIP you received and run the executable on your PC. Follow the on-screen instructions to install it.
Boot your phone into Fastboot mode. Turn off the phone. Press and hold Volume Down + Power simultaneously until the Fastboot screen appears (you’ll see an android icon or “FASTBOOT” text).
Connect your phone to the PC via USB. Use a good quality cable and plug it into a USB port directly on your computer (avoid hubs).
Run the unlock tool. Open the Lenovo Smart Unlock Tool on your PC. It should detect your device. Enter the unlock code you received by email into the tool. Click Unlock.
Confirm the unlock on your phone. The phone will display a warning about unlocking the bootloader. Use the volume keys to select Unlock and press the power button to confirm.
Wait for the process to finish. The phone will reboot automatically. The first boot after unlocking takes longer than usual (up to 10 minutes). Do not interrupt it.
Verify the unlock. After boot, go to Settings > Developer Options and check that OEM Unlocking is now greyed out or shows “Unlocked”. You can also reboot into fastboot and look for “unlocked” text on the bootloader screen.

Common Mistakes

Skipping the backup. Unlocking wipes all data. Many users lose photos and files because they assumed the process wouldn’t erase anything.
Using the wrong USB cable. A charge-only cable will not allow data transfer, so the tool won’t detect your device.
Not enabling OEM Unlocking. If this toggle is off, the unlock tool will fail with an error. Make sure it’s on before starting.
Entering the wrong serial/IMEI. Double-check the numbers you submit to Lenovo. A typo means you’ll get an invalid unlock code.
Interrupting the first boot. Pulling the battery or holding power during the first boot can cause a bootloop.
Using a Mac or Linux. The Lenovo tool is Windows-only. If you’re on another OS, use a Windows PC or a virtual machine with USB passthrough.

Tips

Charge your phone fully. The unlock process takes a few minutes, but a low battery can cause a failure mid-way.
Use the original USB cable that came with the phone if possible—it’s known to work well.
Close other programs on your PC that might interfere with USB connections (like phone sync software).
Keep the unlock code email safe. You may need it again if you ever relock the bootloader.
After unlocking, you can install a custom recovery like TWRP to flash custom ROMs. But do that only after you’ve confirmed the unlock is successful.

Troubleshooting

Tool doesn’t detect my phone. Make sure USB debugging is enabled and the phone is in Fastboot mode. Try a different USB port, reinstall the Lenovo USB drivers, or restart the tool. On Windows, check Device Manager for any unrecognized devices.

OEM Unlocking toggle is greyed out. This usually means the device is carrier-locked or Lenovo hasn’t approved it for unlocking. Check with your carrier, or if you bought it second-hand, the previous owner may have already unlocked it (or locked it again).

Unlock code doesn’t work. Verify you entered the code exactly as in the email—no spaces. If it still fails, re-submit the request on Lenovo’s site, ensuring the serial and IMEI are correct.

Phone stuck in bootloop after unlock. This can happen if the bootloader is unlocked but the stock ROM is incompatible. Try booting into recovery (Volume Up + Power) and performing a factory reset. If that doesn’t help, reflash the stock ROM using Lenovo’s Smart Assistant or QFIL tool.

Phone shows “Your device is corrupt” on boot. This is normal after unlocking. It means the bootloader is unlocked. You can either ignore it or install a custom ROM that suppresses the warning.

Unlock tool crashes. Run it as administrator, and ensure your Windows is up to date. If it still crashes, try a different PC.

Frequently Asked Questions

Will unlocking the bootloader void my warranty? Yes, Lenovo considers bootloader unlocking as modifying the software, which voids the standard warranty. However, you can relock the bootloader later to restore warranty status (if Lenovo allows it for your model).

Does unlocking erase my data? Yes, the unlock process performs a factory reset. You must back up everything beforehand.

Can I relock the bootloader after unlocking? Yes, you can relock it by running the same Lenovo tool and choosing “Lock” (if available) or using fastboot commands. Note that relocking may require the original unlock code.

Is it safe to unlock the bootloader? Unlocking itself is safe if you follow the steps correctly. The risk comes later—if you flash incorrect files, you could brick the device. Always use files meant for the X3A40 model.

Why is my device not eligible for unlocking? Lenovo may block unlocking for devices sold with carrier locks, or if the device’s software is modified (e.g., already rooted). Also, some regions have restrictions.

Do I need a SIM card installed? No, a SIM is not required for the unlock process, but you need the IMEI which is printed on the back of the phone or accessible via *#06#.

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