The EFS Reset Tool is a . It is the defibrillator for your phone's cellular modem—useful in a crisis, but dangerous if used incorrectly. Always backup before you tinker.
Without a functioning EFS partition, your phone essentially loses its identity. It cannot register on a mobile network, meaning you cannot make calls, send SMS texts, or use mobile data. It becomes a small, expensive Wi-Fi-only tablet. efs reset tool