First, get the model ID and CID to get the correct firmware. In order to do it, turn on the LENOVO A850 in the bootloader mode and read all information according to the instructions.
You may also check the model ID by entering the IMEI number on IMEI.info
Once you have model ID and CID, go to Motorola Firmware and select the appropriate model. Then, choose the latest software version(must have the same CID, downgrade not allowed until you not have bootloader unlocked).
After downloading the software, unpack it using any file archiver and copy all the content of the folder into c:\mfastboot where all necessary tools have already been unpacked.
Changing firmware in the phone will erase all of your data.
All described operations you are doing at your own risk.
If want saves your data do a backup before start.
Firmware Update / Change / Repair in LENOVO A850
Launch thecommand line with admin rights.
Go to c:\mfastboot directory
Type cd\ and press enter key.
Type cd mfastboot and press enter key.
Check how many system.img_sparsechunk.* files our firmware has. Usually, it is 3 or 4 files.
Enter the command:
mfastboot devices and press the enter key
to check communication with the LENOVO A850. Please check if what you see on screen is like in the picture, if communication is correct and all drivers instaled you may now install the firmware.
Type commands one by one and approve each of them by pressing Enter.
mfastboot.exe oem lock begin
mfastboot.exe flash partition gpt.bin
mfastboot.exe flash motoboot motoboot.img
mfastboot.exe flash logo logo.bin
mfastboot.exe flash boot boot.img
mfastboot.exe flash recovery recovery.img
Depending on the number of system.img_sparsechunk files present in the firmware folder, do the appropriate number of commands, namely 0-3 or 0-4.
mfastboot.exe flash system system.img_sparsechunk.0
mfastboot.exe flash system system.img_sparsechunk.1
mfastboot.exe flash system system.img_sparsechunk.2
mfastboot.exe flash system system.img_sparsechunk.3
mfastboot.exe flash system system.img_sparsechunk.4
Next, type in the following commands:
mfastboot.exe flash modem NON-HLOS.bin
mfastboot.exe erase modemst1
mfastboot.exe erase modemst2
mfastboot.exe flash fsg fsg.mbn
mfastboot.exe erase cache
mfastboot.exe erase userdata
That's all. Now your LENOVO A850 has a new firmware. To reboot it from the bootloader mode to the normal mode, use this command:
mfastboot reboot and press enter key
Next the LENOVO A850 phone will restart and switch on in a normal mode. It will take between 10-20 minutes.