Code ER95: IO DEVICE
Issue Description & Safety Warning
The Fanuc 30i/31i/32i CNC has triggered a critical IO DEVICE 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
MISMATCH(CHn) (Note3) When this alarm is issued with a machine which has operated normally, possible causes are: (1) The communication cable is broken or a connection failure occurs in the cable. (2) The power to an I/O device is off or is turned on too late. (3) A failure occurs in an I/O device. (4) When the power to the CNC is turned off, then on again, the power to an I/O device is kept on. When turning the power to the CNC off, then on again, be sure to turn the power to all I/O devices off, then on. When this alarm is issued during debugging of a sequence program, there are the following possible causes in addition to the above: (5) The connected I/O device configuration (type, sequence, or number of units) is invalid. (6) An invalid I/O device configuration is registered. When this alarm is issued, any inconsistent I/O device can be checked in the “I/O Device Monitor screen”. This alarm is issued when the I/O devices actually connected to the CNC is inconsistent with the I/O device configurati on registered in the I/O device connection diagnosis screen. All I/O devices connected to the channel for which this alarm was issued are not linked. The ladder program is run even when this alarm is issued.
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 ER95 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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