1. Download and place both the files onto your Desktop.
2. Extract files from the Fastboot archive to your Desktop. Make sure you have adb.exe and fastboot.exe on your Desktop.
3. Rename the CDMA RUU file you just downloaded to PG86IMG.zip.
4. Connect your smartphone to the PC using the USB cable.
5. Transfer the CDMA RUU file to the root folder of your smartphone’s SD card storage.
6. Open a Command Prompt Window on the Desktop of your PC. Press and hold the Shift key on your keyboard and right-click on any empty area on the screen and choose Open command window here.
7. Issue the following command using the Command Prompt Window:
adb reboot recovery
8. Your device should reboot into the recovery mode.
9. Using the options given in the Recovery menu, wipe Dalvik, cache, data, system and factory reset.
10. Reboot your device.
11. Now, issue the following command using the same Command Prompt Window:
adb reboot bootloader
12. Your smartphone should automatically detect the RUU file and ask you if you want to flash it. Hit the Yes option.
13. After the file has been flashed on your device, choose the Fastboot mode from the bootloader menu.
14. Type in the following command into the Command Prompt Window:
fastboot oem lock
15. It should relock the bootloader of your device. Enter the following command to reboot your device.
fastboot reboot
16. You are good to go !
Your smartphone has been successfully unrooted and the bootloader is also relocked.