An is a user-defined or builder-defined alarm that originates from the PLC (Programmable Logic Controller) inside the machine. While the CNC control (Fanuc, Mitsubishi, or Siemens) handles axis movement and spindle speed, the PLC handles the "body" of the machine: coolant pumps, chip conveyors, door locks, hydraulic units, tool changers, and safety interlocks.
The coolant tank level has dropped below the minimum sensor threshold. EX0451 (Spindle Lube Alarm): mori seiki ex alarm list