What Is EFS File In Android Firmware
the full name of efs file in Android Firmware “Encrypting file System” .It stores information like imei, serial number, configuration, diag settings and radio settings etc.in encrypted format in file system level firmware.
If the efs file becomes corrupt for some reason. So this imei information does not come from the mobile phone or there is a problem of base-band unknown, radio signal etc. Because of which network signal does not come in the mobile phone.
How will you loss the EFS folder
As far as I know, you always lose your EFS by incorrect operation. For example, erasing ROM or Flash data using an unqualified method. Even starting the wrong way like direct ejecting the battery to turn off the mobile phone can also contaminate your EFS.
Roaming routes and flashing usually have no effect on EFS data, but you know that the actual word can have everything. There are a few ways you can check if your EFS folder is lost: inputting * # 06 # on the dialer, going to Settings / Phone / Status or checking the MAC address.
How to Backup EFS folder ?
There are many tools that you can use to back up an EFS folder. They all work in a similar way. Eg mircel box, umt, z3x