The Fanuc 0i-Model B (0i-B) is the second-generation 0i controller and, like the 0i-A, reports alarms as plain numeric codes. Here are the alarms seen most often on 0i-B machines, with causes and fixes.
How 0i-B Alarm Numbers Map
- 000–199 — Program / parameter • 300s — APC (encoder)
- 400s — Servo • 500s — Overtravel • 700s — Overheat / spindle • 900+ — System
Common 0i-B Alarms
| Alarm | Meaning | Common Cause & Fix |
|---|---|---|
| 000 | Please turn off power | Power-cycle after a parameter change. |
| 100 | Parameter write enable | Set PWE = 0 on the SETTING screen and RESET. |
| 300 | APC alarm — reference return required | ABS position lost after a battery change. Perform zero-return. |
| 401 | Servo amplifier VRDY OFF | Amp not ready — check DC link, E-stop, amp power and fault LED; repair/replace drive. |
| 404 | VRDY signal ON (stuck) | Faulty servo amplifier or wiring. |
| 410 / 411 | Excessive position error (stop / move) | Bind, overload, encoder or amplifier/motor fault. |
| 414 | Digital servo system fault | Check amplifier alarm code, motor and feedback. |
| 417 | Illegal digital servo parameter | Restore parameters; replace CNC battery A98L-0031-0025. |
| 500 / 501 | Stored stroke limit + / − exceeded | Jog back inside range and reset. |
| 700 | Overheat: control unit | Check cabinet cooling fan and ambient temperature. |
| 704 | Spindle speed fluctuation / overheat | Overload, belt slip, motor or spindle amplifier fault. |
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Quick-reference of common alarms. For the complete list, refer to the Fanuc 0i-B Maintenance Manual.