FANUC Alarm PRIO-021 — SYST Unknown I/O hardware
Error- Hardware
- I/O Link and process I/O
- Controllers
- R-J3iB / R-30iA
- FANUC class
- SYSTEM
- Hardware family
- FANUC I/O Link, process I/O board, fuse and output alarms
FANUC PRIO-021 (“SYST Unknown I/O hardware”): An unknown device is connected to the I/O Link connector. First check: Replace the device with a device that is compatible with the current software or install a version of software that recognizes the device.
Updated 2026-10-22 · LogrobotLM reference
Description
An unknown device is connected to the I/O Link connector. This device is not recognized by the current controller software version.
Remedy
Replace the device with a device that is compatible with the current software or install a version of software that recognizes the device.
Field diagnosis
A module connected to the I/O Link is not recognized by the controller software version.
What to check
- Replace the module with a supported model, or update the controller software.
- Note: Common with a replacement module that is more recent than the cabinet.
Related codes
Indicative field information — the robot manufacturer's manual and safety procedures always prevail. Never bypass a safety device; apply lockout/tagout (LOTO) before any physical intervention. How this reference is built →