The Fanuc 31i-Model A is part of the high-end Series 30i/31i/32i family used on multi-axis, multi-path machining centres and lathes (including 5-axis work). It uses the modern letter-prefix alarm structure. Here are the codes seen most often, with causes and fixes.
31i-A Alarm Prefixes
- PS — Program / setting • SV — Servo • SP — Spindle
- OT — Overtravel • OH — Overheat • APC/DS — Encoder • SR — Serial
Common 31i-A Alarms
| Alarm | Meaning | Common Cause & Fix |
|---|---|---|
| PS0000 | Please turn off power | Power-cycle after a parameter change — switch OFF then ON. |
| PS0100 / PS0101 | Parameter write enable / clear memory | Set PWE = 0 and RESET; for PS0101 power on holding RESET + DELETE (back up first). |
| SV0401 | Servo amplifier VRDY OFF | Amp not ready — check DC link, E-stop, amp power and fault LED; repair/replace drive. |
| SV0410 / SV0411 | Excessive error (stop / move) | Bind, overload, low gain or amplifier/motor fault on the indicated axis. |
| SV0417 | Illegal digital servo parameter | Restore servo parameters; replace CNC battery A98L-0031-0025. |
| SV0436 | Soft thermal (OVC) | Overload/blocked cooling — check fans and mechanical load. |
| SV0445 / SV0447 | Encoder disconnect (soft / hard) | Inspect feedback cable; replace a faulty encoder. |
| SP (spindle) | Serial spindle alarm | Read the amplifier code — see our Alpha-i drive alarm guide. |
| OT0500 / OT0501 | Stroke limit + / − exceeded | Jog back inside travel and reset. |
| OH0700 | Control unit overheat | Check cabinet cooling fan and ambient temperature. |
| APC0300 / APC0301 | Reference return required / APC comms | Redo zero-return after battery change; check encoder cable & battery. |
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Quick-reference of common alarms. For the complete list, refer to the Fanuc Series 30i/31i/32i Maintenance Manual.