Code PS1820 / BG1820 / SR1820: ILLEGAL DI SIGNAL STATE
Issue Description & Safety Warning
The Fanuc 0i-D / 0i Mate-D Alarm List has triggered a critical ILLEGAL DI SIGNAL STATE alarm. Immediate attention from a qualified operator or maintenance technician is required to prevent secondary damage to the equipment or spoiled parts during the manufacturing cycle. Always ensure standard safety and LOTO procedures are followed before accessing electrical cabinets.
Official Troubleshooting Steps
Section: CNC alarm list Alarm group: Program/operation, background edit, communication (PS/BG/SR common alarm number) Original alarm number: 1820 1) An each axis workpiece coordinate system preset signal was turned “1” in the state in which all axes on the path including the axis on which to perform preset with the each axis workpiece coordinate system were not stopped or in which a command was in execution. 2) When the M code for performi ng preset with an each axis workpiece coordinate system pres et signal is specified, the each axis workpiece coordinate system preset signal is not input. 3) The auxiliary function lock is enabled.
Source: Fanuc B-64305EN/03 Appendix A Alarm List
Last reviewed: 2026-07-01 · Verified against the manufacturer’s official documentation.
About Fanuc 0i-D / 0i Mate-D Alarm List Alarms
Fanuc controllers include extensive self-diagnostics that flag or halt the machine when a fault is detected. Error code PS1820 / BG1820 / SR1820 on the 0i-D / 0i Mate-D Alarm List identifies one specific fault condition — its documented cause and the official corrective steps are listed above, sourced from Fanuc's service documentation. Always confirm against the manual for your exact machine configuration and follow LOTO procedures before servicing.
Complete Alarm List: 769 Fanuc 0i-D / 0i Mate-D Alarm List codes.
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