Before attempting advanced repairs, verify the current status of your device:
: This standard code displays your current IMEI on the screen.
: The device may stop recognizing its own serial identifier, preventing it from registering on mobile networks.
: Custom ROM installations or manual firmware downgrades can corrupt the EFS (Encrypted File System) partition where the IMEI is stored.
: Without a valid IMEI, the phone cannot make calls or use mobile data. Diagnostic Tools and Verification