The proprietary %XPOFWARN command controls the power off warnings from the modem. v2.0.x
%XPOFWARN is based on voltage level detection without any delay. When this
warning has been sent once, it needs to be enabled again by sending
AT%XPOFWARN=1,<voltage>.
%XPOFWARN is enabled by default at the 3000 mV level. Active %XPOFWARN warning blocks the storing to NVM.
For a detailed description of the nRF91x1 power supply monitoring functionality, see Power supply monitoring in nRF9131 Product Specification and nRF9161 Product Specification.