A Fanuc 0i-Model D (0i-D / 0i Mate-D) controller displays an alarm whenever it detects a fault in the CNC, servo, spindle or I/O system. Knowing what each code means saves hours of downtime. Below are the most commonly seen 0i-D alarms with their causes and practical fixes.
How Fanuc 0i-D Alarm Codes Are Structured
Unlike older controllers, the 0i-D shows each alarm with a letter prefix that tells you the system area, followed by a number. The main groups are:
- PS — Program / setting (parameter) alarms
- SV — Servo alarms
- SP — Spindle alarms
- OT — Overtravel (stroke limit) alarms
- OH — Overheat alarms
- APC / DS — Absolute Pulse Coder (encoder) alarms
- SR — Serial communication (RS-232) alarms
- SW / PW — Power / parameter-switch alarms
Common Program / Setting (PS) Alarms
| Alarm | Meaning | Common Cause & Fix |
|---|---|---|
| PS0000 | Please turn off power | A parameter that needs a power cycle was changed. Turn the machine OFF and ON again. |
| PS0010 | Improper G-code | An unusable or wrong G-code is in the program. Correct the part program. |
| PS0090 | Reference return incomplete | Zero return could not finish (axis too close to grid, low speed, or encoder issue). Move the axis away from the reference point and retry. |
| PS0100 | Parameter write enable | Parameter Write (PWE) is set to 1 on the SETTING screen. Set PWE = 0 and press RESET. |
| PS0101 | Please clear memory | A parameter needing a memory clear was changed. Power on while holding RESET + DELETE (back up parameters first). |
Common Servo (SV) Alarms
| Alarm | Meaning | Common Cause & Fix |
|---|---|---|
| SV0401 | Servo amplifier VRDY (ready) signal OFF | Amplifier not ready — check DC link voltage, E-stop, amplifier power and the amplifier fault LED. Repair/replace the servo drive if faulty. |
| SV0404 | VRDY signal ON (stuck) | Ready signal stays on when it should be off. Usually a faulty servo amplifier or wiring fault. |
| SV0410 | Excessive error at stop | Position error too large while stopped — mechanical bind, low servo gain, or amplifier/motor fault. |
| SV0411 | Excessive error during movement | Position error too large while moving — overload, encoder fault, or amplifier issue. |
| SV0417 | Illegal digital servo parameter | Servo parameters corrupted (often after a battery failure or board change). Restore from backup; replace the CNC battery A98L-0031-0025. |
| SV0436 | Soft thermal (OVC) | Software thermal model tripped — overload or blocked cooling. Check cooling fans and mechanical load. |
| SV0445 / SV0447 | Soft / Hard encoder disconnect | Feedback signal lost. Inspect the encoder cable and connectors; replace a faulty encoder. |
Common Overtravel (OT) & Overheat (OH) Alarms
| Alarm | Meaning | Common Cause & Fix |
|---|---|---|
| OT0500 / OT0501 | Stored stroke limit + / − exceeded | Axis moved past the soft limit. Jog back inside the travel range and reset. |
| OT0506 / OT0507 | Hardware overtravel + / − | A hardware limit switch is tripped. Release the switch (hold OT-release) and jog clear. |
| OH0700 | Control unit overheat | Cabinet/control too hot. Check the cabinet cooling fan and ambient temperature. |
| OH0701 | Fan motor overheat / failure | Internal fan stopped. Replace the controller fan (e.g. Fanuc fans). |
Encoder (APC) & Serial (SR) Alarms
| Alarm | Meaning | Common Cause & Fix |
|---|---|---|
| APC0300 | Reference return required (APC alarm) | Absolute position lost after battery change. Perform the zero-return / referencing procedure. |
| APC0301 | APC communication error | Encoder/serial fault. Check encoder cable and battery; replace encoder if needed. |
| SR0085 / SR0086 / SR0087 | RS-232 reader/punch error | Baud rate, framing or cable problem during DNC/transfer. Match communication settings on both ends. |
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This is a quick-reference of commonly encountered alarms. For the complete official code list, always refer to the Fanuc 0i-D Maintenance Manual.