119

Power cycle the control completely (turn off main power for 30 seconds). On startup, observe if alarm persists immediately after boot or during initialization. If alarm occurs during boot sequence, system ROM is likely corrupted.

Ensure machine is in safe state and all axes are secured before power cycling

Check battery voltage at DIAGNOSIS > BATTERY screen or measure directly on control board. Voltage should be above 3.0V for proper memory retention. Low battery during system updates can corrupt Flash memory.

Attempt system software reload using Fanuc BOOT/DOS floppy or USB method. Access SYSTEM > BOOT MODE by holding DELETE and INPUT keys during power-on. Reload system software from backup media or Fanuc distribution files matching exact control series and version.

System reload will restore factory software - ensure all parameters, ladder, and PMC are backed up before proceeding

If software reload fails or alarm persists, contact Fanuc for ROM module replacement or motherboard repair. Document exact control model, serial number, and system software version from SYSTEM > VERSION screen before contacting support.

Inspect control cabinet for environmental issues: check cooling fan operation, verify ambient temperature below 45°C, and ensure no dust accumulation on PCB boards. Overheating can cause intermittent memory errors.

Check LED indicators on main CPU board. Most Fanuc boards have LED diagnostic codes during boot. Refer to hardware manual for specific board type (e.g., A20B-8200-series). Continuous red LED or specific flash patterns indicate hardware fault.

Use ESD precautions when opening control unit - ground yourself before touching PCB boards

If control has been subjected to power surge or electrical noise, inspect for visible PCB damage, burnt components, or swollen capacitors on main board and power supply unit. Check control ground resistance to machine frame (should be less than 0.1 ohm).

Replace main CPU board if hardware failure confirmed. Ensure replacement board matches exact part number and revision. After replacement, reload all system software, parameters, PMC ladder, and macro programs from backup.

New CPU boards require system initialization and parameter restoration - machine will not operate without proper setup

If alarm occurred immediately after attempted system update or option installation, attempt to re-enter BOOT MODE (hold DELETE and INPUT during power-on) to access system recovery functions. Select INIT+LOAD option to clear corrupted files.

INIT+LOAD will erase all user data - only use if control is non-functional

Using BOOT MODE, reload complete system package from Fanuc original media. Ensure software version matches control series exactly (verify on control nameplate: 0i-MF, 31i-B5, etc.). Use only Fanuc-certified CF cards or USB devices formatted FAT32.

After successful system reload, verify system integrity at SYSTEM > PARAM screen. Check parameter 0000 (control type) and 0001 (series/version) match expected values. Navigate to SYSTEM > OPTION and verify all purchased software options are enabled correctly.

Restore all backed-up parameters, PMC ladder, and custom macros. Perform full machine initialization including PMC reset and reference position return. Test all axes and functions before returning to production.