Code WN69: I/O Link i DO ALARM
Issue Description & Safety Warning
The Fanuc 30i/31i/32i CNC has triggered a critical I/O Link i DO ALARM 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
(CHn Gxx Syy zz: PMCm Ybbb = **H ) (Note1) Check DO of the relevant device. The DO alarm (ex. a short circuit with the ground) occurs at “zz” bytes of slot “yy” of group “xx” in channel “n”. Y “bbbb” of PMC path ”m” is the address at which the alarm occurred. DCSPMC Y”bbbb” is the address for DCSPMC. Display of “PMC*Y****” is the case of occurrence of unassigned address. The “**H” shows some bits at which the alarm occurs by hexadecimal. (Ex. “PMC1Y115=28H” shows the alarm occurs at Y115.3 and Y115.5 in PMC1. “28H” means “00101000” in binary. ) For the details of the alarm of I/O devices, refer to the “Connection manual (HARDWARE) (B-64483EN)”.
Source: Fanuc Series 30i/31i/32i-A Maintenance Manual, Appendix A Alarm List — PMC alarms (B-64485EN/01)
Last reviewed: 2026-07-01 · Verified against the manufacturer’s official documentation.
About Fanuc 30i/31i/32i CNC Alarms
Fanuc controllers include extensive self-diagnostics that flag or halt the machine when a fault is detected. Error code WN69 on the 30i/31i/32i CNC 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: 85 Fanuc 30i/31i/32i CNC codes.
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