Although the LG Leon has been launched a few months ago, the device has already received the latest Android 5.1.1 Lollipop firmware. T-Mobile has pushed quite a few updates to its LG Leon variant lately, making it stable than ever. If for some reason you have installed a custom ROM and want to revert back to the stock one, or just want to flash the latest available stock firmware (H345) on your LG Leon, then this is what the tutorial is all about.

The firmware comes in the form of a .kdz extension which needs to be flashed onto your device with the available LG Flash Tool. Using this tool you can upgrade, downgrade or re-flash the stock firmware to your LG device. This method will also work with other LG Leon variants including the T-Mobile LG Leon 4G LTE. Following this tutorial will also unroot your device and also lock the bootloader.

Moreover, with this tutorial, you can install the stock firmware of your choice. The latest available firmware which is based on Android 5.1.1 Lollipop software version. You can get this firmware from the website listed below or from the official T-Mobile portal.


  • Download the T-Mobile LG Leon Firmware. You can find it by searching on the Internet. However, in order to download it, IMEI number is required. Get your IMEI from the box that came with the handset, or dial *#06# from your handset. Once you have your IMEI number, paste it in the text panel and your firmware will be downloaded. If you are not able to recover your IMEI number.
  • Install the LG Flash Tool 2014(extract files if compressed) on your PC. This tool is required in order to flash the KDZ file onto your device.
  • Visual C++ Runtime Library is required in order to run LG Flash Tool 2014. If you have any problems installing or running the Flash Tool then install the libraries on your Windows PC. Click here.
  • Make sure you have the latest LG drivers installed on your PC. Get it from the download section.


Download | LG Flash Tool 2014

Download | T-Mobile LG Leon drivers

Backup Your Apps and Data

Installing the stock firmware using a KDZ file will remove all your data and apps from your current ROM. So make sure you have a backup of all your apps and data. Also transfer all your files from your internal storage to your PC as it may also get wiped out.

Install Stock Firmware on T-Mobile LG Leon using KDZ file

Here is a step-by-step guide to successfully flash the stock firmware on your T-Mobile LG Leon.

  • Step 1: Put your phone into Download Mode. To do this, Power Off your phone and while pressing both the volume keys connect your phone to your PC via USB cable. The screen will show download mode icon. Let drivers be installed on your PC. If it fails for first time repeat the process (try pressing just the Volume Up key).
  • Step 2: Open the LG Flash Tool 2014 folder and copy the KDZ file in it. If the Flashtool is compressed, extract it to get a folder containing the necessary files including the LGFlashtool2014.exe file. Transfer the .kdz file, you have just downloaded, into the LG Flash Tool 2014 folder.
  • Step 3: Run LGFlashtool2014.exe file.


  • Step 4: Now you will have to make a bunch of selections. Select Type: 3GQCPT (Do not worry about selecting this option as Flashtool is modified only for devices with SIM). Change PhoneMode to CS_EMERGENCY. Click the folder icon to browse your computer and select the .kdz file.
  • Step 5: Choose CSE Flash option as we are installing a new copy on the stock firmware. This will format all your application data, format your system and could also wipe your internal storage. It makes a clean install. If you choose this method, it is highly recommended that you backup all your apps and data first. (Normal Flash option should be selected if you are on stock firmware and you just want to upgrade and do not want to lose any data.)
  • Step 6: Once selected, choose Start on next window.


  • Step 7: Select your Region and Language and select OK button. Also clear phone for update registry.

Note: Disconnect from the internet before you choose OK and also make sure your Antivirus is turned off for some time.


  • Step 8: Once the program has started, the stock firmware will get installed.


  • Step 9: If in case an error occurs, retry from Step 1 until success and remember to disconnect from the internet when necessary. Once successful, the phone will restart automatically and choose click exit to quit the program.
  • Step 10: Once you see the LG Logo, that means you have installed the stock firmware correctly.

Once you boot your T-Mobile LG Leon, you can enjoy your stock firmware. For any queries, comment down below.

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