This page covers FANUC IO alarms related to file systems, memory access, and program storage, as well as PW alarms related to power-off required conditions, parameter setting faults, and PMC address assignment errors. These alarm groups are important because they are connected to CNC data handling, parameter integrity, control configuration, and machine restart requirements.
These alarm references apply to FANUC Series 0i-Model D and FANUC Series 0i Mate-Model D.
In practical service work, IO alarms often point to problems involving the CNC file system, program storage memory, or tool data management, while PW alarms are more commonly associated with parameter changes, address definition errors, compensation settings, and machine conditions that require power cycling before normal operation can continue. At REACO CNC, we supply FANUC CNC parts, FANUC robot parts, Mitsubishi automation parts, and repair services for customers worldwide.
What These FANUC IO and PW Alarms Usually Indicate
This section of the FANUC alarm list focuses on CNC internal data handling and configuration control. IO alarms usually indicate that the control cannot correctly access a file system, program storage area, or related memory resource. In practical terms, this can affect program storage, file access, tool life management, or other CNC data functions.
PW alarms, by contrast, usually indicate that the CNC has detected a condition requiring the power to be turned off, or that parameter and PMC-related settings are incorrect. These alarms are often seen after parameter changes, configuration work, compensation setup, spindle assignment adjustments, or PMC signal definition errors. Because some PW alarms are tied to system structure and configuration logic, they often require a careful review of settings rather than simple alarm clearing.
Common Causes of FANUC IO and PW Alarms
Typical causes of IO alarms include file system abnormalities, memory checksum errors, invalid memory access, or internal CNC storage issues affecting program data and related functions. In some cases, the control may still operate in other areas while a specific file or memory-related operation fails.
Typical causes of PW alarms include parameter changes that require a power cycle, incorrect PMC address assignment, invalid signal allocation, improper compensation settings, servo spindle parameter mismatch, or other configuration values outside the allowed range. On some machines, these alarms may appear after maintenance, retrofit work, parameter restoration, or changes to spindle or PMC-related setup data.
Full FANUC IO Alarm List: File System and Memory Alarms
Table 1. File System and Program Memory Alarms
| Alarm Code | Alarm Message | Full Technical Content |
|---|---|---|
| IO1001 | File access error | Due to an abnormality in the CNC file system (resident type), the resident file system cannot be accessed. |
| IO1002 | File system error | Due to an abnormality in the CNC file system, files cannot be accessed. |
| IO1030 | Program checksum error | The checksum of the memory used for CNC program storage is incorrect. |
| IO1032 | Memory access out of range | Access outside the range of memory used for CNC program storage occurred. |
| IO1104 | Tool life management exceeds maximum group count | The maximum number of tool life management groups in the system has been exceeded. Correct the setting of the maximum group count in parameter (No.6813). |
Full FANUC PW Alarm List: Power-Off Required and Configuration Alarms
Table 2. General Power-Off Required and PMC Address Alarms
| Alarm Code | Alarm Message | Full Technical Content |
|---|---|---|
| PW0000 | Power must be turned off | A parameter that requires the power to be temporarily turned off has been set. |
| PW0001 | Undefined X address | The PMC X address could not be assigned correctly. Possible cause: during the setting of parameter (No.3013), the X address for the reference return deceleration dog (*DEC) was not assigned correctly. |
| PW0002 | PMC address incorrect (axis) | The address assigned to axis signals is incorrect. Possible cause: parameter (No.3021) is set incorrectly. |
| PW0003 | PMC address incorrect (spindle) | The address assigned to spindle signals is incorrect. Possible cause: parameter (No.3022) is set incorrectly. |
| PW0006 | Power must be turned off (malfunction prevention function) | The malfunction prevention function detected an alarm that requires power-off. |
| PW0007 | Cannot define X address (skip) | The PMC X address could not be assigned correctly. Possible causes include: 1) during the setting of parameter (No.3012), the X address for the skip signal was not assigned correctly; 2) during the setting of parameter (No.3019), signals other than skip were not assigned correctly to the X address. |
Table 3. Compensation, Spindle and PMC Parameter Setting Alarms
| Alarm Code | Alarm Message | Full Technical Content |
|---|---|---|
| PW1102 | Illegal parameter (inclination compensation) | The parameter settings for inclination compensation are incorrect. Possible causes include: 1) compensation points are not numbered in order; 2) the compensation points are not located between the most negative and most positive pitch error compensation points; 3) the compensation amount specified for each compensation point is too large or too small. |
| PW1110 | Parameter setting error (servo motor spindle) | The parameter settings for a spindle control axis based on a servo motor are incorrect. |
| PW1111 | Spindle number incorrect (servo motor spindle) | For a spindle control axis based on a servo motor, the spindle number (No.11010) or spindle amplifier number (No.3717) is set incorrectly. |
| PW5046 | Illegal parameter (straightness compensation) | [M] The parameter settings for straightness compensation are incorrect. |
| PW5390 | PMC R address setting incorrect | The range or start address of the PMC R address set by parameter (No.3773) is incorrect. |
Practical Inspection Notes
When an IO alarm appears, the first practical step is usually to determine whether the problem is limited to file access, program storage, or a broader control memory issue. If the alarm is related to checksum error, memory range violation, or repeated file access failure, it is often important to review recent data operations, stored programs, backup history, and the condition of the control before making further changes.
When a PW alarm appears, it is usually helpful to confirm whether parameters were recently modified and whether the machine now requires a power cycle to apply those settings correctly. For PMC address-related alarms, the signal allocation and related parameter numbers should be reviewed carefully. For compensation and spindle-related PW alarms, the relevant parameter structure, numbering logic, and matching relationships should also be checked before restarting the machine.
REACO CNC Support
REACO CNC supplies FANUC CNC parts, FANUC robot parts, Mitsubishi automation parts, and repair services for customers worldwide. If your machine is showing IO or PW alarms related to file access, memory handling, parameter settings, spindle configuration, or PMC address allocation, we can support your spare parts sourcing and industrial repair requirements.
With 34 years of industry experience, REACO CNC supports global customers with worldwide shipping, tested industrial parts, and practical repair solutions for FANUC and Mitsubishi systems.
FAQ
What does a FANUC IO alarm usually mean?
It usually means the CNC detected a problem involving file access, the internal file system, program storage memory, or a related data handling function.
What does a FANUC PW alarm usually mean?
It usually means the control detected a condition requiring the power to be turned off, or that a parameter, signal allocation, or configuration setting is incorrect.
Why does PW0000 appear?
PW0000 appears when a parameter has been set that requires the machine power to be temporarily turned off.
What should be checked for PMC address related alarms?
Typical checks include the relevant PMC address assignment parameters, signal allocation logic, address range, and whether the related X or R addresses were defined correctly.
Which machines does this reference apply to?
These alarm references apply to FANUC Series 0i-Model D and FANUC Series 0i Mate-Model D.
Reference Source: Beijing FANUC. This article is based on technical documentation provided by Beijing FANUC.
For More Fanuc CNC repair Cases and technical articles, please back to Fanuc Technical Support Center.
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