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Power down the CNC completely and check all connections to the main CPU board. Inspect for physical damage, corrosion, or burn marks on the CPU board near memory ICs.

Disconnect all power including battery backup before inspecting internal components.

If board appears physically intact, attempt a cold restart: disconnect AC power for 10 minutes, discharge residual voltage, reconnect and power up to verify if error persists.

Navigate to SYSTEM > DIAGNOSIS screen and check for additional memory-related diagnostic alarms or status indicators that may confirm hardware failure.

Replace the main CPU board with a compatible unit for your control series (0i-MD, 0i-MF, 16i/18i/21i, 30i/31i/32i). After replacement, reload all parameters from backup using SYSTEM > PMC > I/O and SYSTEM > PARAM functions.

Ensure exact model compatibility and transfer CNC parameters, PMC ladder, and pitch error compensation data from backup before returning to operation.

Check the control power supply unit voltages using SYSTEM > MAINTENANCE > VOLTAGE display. Verify +5VDC, +24VDC, and other supply rails are within ±5% tolerance per Fanuc specifications.

Inspect grounding connections at the control cabinet. Verify control ground (FG), signal ground (SG), and earth ground connections are secure with resistance below 0.1 ohms.

Poor grounding can cause intermittent memory errors and other electronic malfunctions.

Check for EMI sources near the control cabinet including welders, VFDs, or high-current switching equipment. Relocate or shield sources if found within 2 meters of CNC cabinet.

If voltage irregularities are detected, replace the control power supply unit (PSU) with OEM Fanuc unit. Re-test system after PSU replacement and monitor for recurring alarms.

Check battery voltage at SYSTEM > MAINTENANCE > BATTERY screen or measure directly at battery terminals. Replace if below 3.0V (lithium) or 2.7V (alkaline) depending on control series.

Low battery voltage (BAT ALARM) should be addressed immediately to prevent parameter loss.

If battery was completely depleted, attempt to clear all alarms and perform a full system reboot. Navigate to SYSTEM > INIT/CLEAR and execute a partial initialization if alarm persists after reboot.

Initialization will clear certain system data. Ensure parameter backup is available before proceeding.

If alarm continues after battery replacement and cold restart, DRAM hardware failure is confirmed. Proceed with main CPU board replacement as primary solution.