This page covers FANUC SV alarms related to FSSB communication, servo initialization, axis assignment, tandem drive settings, configuration mismatches, and servo setup errors. These alarms are especially important during machine commissioning, control replacement, amplifier replacement, parameter restoration, software changes, and troubleshooting after wiring or configuration work.
These alarm references apply to FANUC Series 0i-Model D and FANUC Series 0i Mate-Model D.
In practical maintenance work, these alarms often indicate that the CNC, amplifier, axis card, servo software, or axis allocation settings are not aligned correctly. Unlike pure overheat or current alarms, this group is more closely related to system structure, initialization sequence, configuration logic, and parameter consistency. At REACO CNC, we support global customers with FANUC CNC parts, FANUC robot parts, Mitsubishi automation parts, and industrial repair services.
What These FANUC SV Alarms Usually Indicate
This section of the FANUC SV alarm list mainly relates to system-level servo setup conditions. In real applications, these alarms may appear when the CNC cannot complete servo initialization correctly, when the FSSB network cannot open normally, when the number or type of connected amplifiers does not match the configured values, or when axis numbers and tandem relationships are assigned incorrectly.
These alarms are also common after replacing amplifiers, changing axis cards, restoring parameters, modifying servo-related settings, or rebuilding a machine control system. In many cases, the hardware itself is not completely failed; the problem may instead be caused by an incorrect configuration, mismatched amplifier type, duplicate axis number, invalid parameter setting, or abnormal initialization path.
Common Causes of FANUC FSSB and Servo Setup Errors
Typical causes include incorrect servo axis assignment, duplicate or out-of-range axis numbers, wrong tandem control settings, mismatch between connected amplifier type and configured FSSB settings, failure to read amplifier ID information at power-on, optical cable problems, axis card issues, or incomplete servo initialization.
These alarms may also be seen when the control software and hardware combination is incorrect, when a machine has been retrofitted or repaired using a different amplifier or module, or when parameters related to straightness compensation or servo allocation have been entered incorrectly. For this reason, this group of alarms often requires a broader configuration review instead of checking only one component.
Full FANUC SV Alarm List: FSSB, Axis Configuration and Servo Setup Errors
Table 1. Servo Initialization and Ready Signal Alarms
| Alarm Code | Alarm Message | Full Technical Content |
|---|---|---|
| SV1025 | V-ready signal abnormal (initialization) | When servo control is turned on, the speed control ready signal (VRDY) should be off, but it is already on. |
| SV0401 | Servo V-ready signal off | The position control ready signal (PRDY) is on, but the speed control ready signal (VRDY) is off. |
| SV0404 | Servo V-ready signal on | The position control ready signal (PRDY) is off, but the speed control ready signal (VRDY) is on. |
Table 2. Axis Assignment, Tandem Control and Servo Parameter Setup Alarms
| Alarm Code | Alarm Message | Full Technical Content |
|---|---|---|
| SV1026 | Illegal axis assignment | The servo axis arrangement parameters have not been set correctly. In parameter (No.1023), “servo axis number for each axis,” a negative value, duplicate value, or a value larger than the number of controlled axes has been set. |
| SV1055 | Dual motor drive axis incorrect | In tandem control, the setting of parameter (No.1023) is incorrect. |
| SV1056 | Dual motor drive axis pair setting incorrect | In tandem control, the setting of TDM (No.1817#6) is incorrect. |
| SV0417 | Illegal digital servo parameter | The digital servo parameter settings are incorrect. When diagnostic information No.203#4=1, the servo software detected an illegal parameter. Use diagnostic information No.352 to determine the cause. When diagnostic information No.203#4=0, the CNC software detected an illegal parameter. Possible causes include: 1) a motor model value outside the specified range has been set in parameter (No.2020); 2) the motor rotation direction in parameter (No.2022) has not been set correctly (111 or -111); 3) parameter (No.2023) for velocity feedback pulses per motor revolution has been set to an invalid value below 0; 4) parameter (No.2024) for position feedback pulses per motor revolution has been set to an invalid value below 0. |
| SV0456 | Illegal current loop | The configured current control cycle cannot be set. The amplifier pulse module used is not suitable for high-speed HRV, or the system does not satisfy the conditions required for high-speed HRV control. |
| SV0458 | Current loop error | The configured current control cycle differs from the actual current control cycle. |
| SV0459 | High-speed HRV setting error | In the two adjacent axes specified by servo axis number (parameter No.1023), one of the odd/even axis pair can perform high-speed HRV control, while the other cannot. |
| SV0468 | High-speed HRV setting error (AMP) | High-speed HRV has been set for an axis controlled by an amplifier that does not support high-speed HRV. |
| SV0466 | Motor / amplifier combination incorrect | The maximum current value of the amplifier and the maximum current value of the motor do not match. Possible causes include: 1) incorrect assignment of axis and amplifier connection; 2) incorrect setting of parameter (No.2165). |
| SV1100 | Straightness compensation overflow [M] | The straightness compensation value exceeded the maximum value of 32767. |
Table 3. FSSB Communication, Amplifier Recognition and Configuration Alarms
| Alarm Code | Alarm Message | Full Technical Content |
|---|---|---|
| SV0460 | FSSB disconnection | FSSB communication was suddenly disconnected. Possible causes include: 1) the FSSB communication cable is disconnected or broken; 2) amplifier power was suddenly shut off; 3) the amplifier issued a low-voltage alarm. |
| SV0462 | CNC data transfer error | Due to an FSSB communication error, correct data cannot be received on the driven side. |
| SV0463 | Slave data transmission failed | Due to an FSSB communication error, the servo software cannot receive correct data. |
| SV0465 | ID data read failed | At power-on, the initial ID information of the amplifier could not be read. |
| SV0604 | Amplifier communication error | Communication abnormality occurred between the servo amplifier and the common power supply. |
| SV1067 | FSSB: configuration error (software) | An FSSB configuration error (software detection) occurred. The connected amplifier type differs from the FSSB setting value. |
| SV5134 | FSSB: power-on timeout | During initialization, FSSB did not enter the ready-open state. The axis card may be defective. |
| SV5136 | FSSB: insufficient amplifiers | Compared with the number of controlled axes, the number of amplifiers recognized by FSSB is insufficient. The axis count setting or amplifier connection is incorrect. |
| SV5137 | FSSB: configuration error | An FSSB configuration error occurred. The connected amplifier type differs from the FSSB setting value. |
| SV5139 | FSSB: error | Servo initialization did not end normally. Possible causes include defective optical cable or incorrect connection between the amplifier and other modules. |
| SV5197 | FSSB: power-on timeout | Although the CNC permitted FSSB to open, FSSB did not open. Check the connection status between the CNC and the amplifier. |
Table 4. Hardware and Software Combination Alarm
| Alarm Code | Alarm Message | Full Technical Content |
|---|---|---|
| SV0403 | Hardware / software mismatch | The combination of the axis card and servo software is incorrect. Possible causes include: 1) the correct axis card has not been installed; 2) the correct servo software has not been installed in flash memory. |
Practical Inspection Notes
When this group of SV alarms appears, the first step is usually to review the machine’s configuration rather than immediately replacing hardware. In many cases, the root cause is found in servo axis numbering, tandem settings, amplifier type mismatch, incomplete initialization, or FSSB communication path problems. It is often helpful to compare the actual machine structure with the configured parameters, amplifier arrangement, and installed control modules.
For FSSB-related alarms, practical checks usually include the optical cable condition, amplifier power status, amplifier order, module connection, axis card condition, and whether the connected amplifier types match the configured values. For axis configuration and tandem alarms, it is important to verify servo axis number assignments, duplicated values, parameter range validity, and whether master/slave relationships have been defined correctly. After control replacement or parameter restoration, these checks become especially important.
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 FSSB alarms, servo setup errors, axis assignment problems, or amplifier configuration mismatches, we can support your parts sourcing and repair needs for FANUC industrial automation systems.
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 equipment.
FAQ
What does an FSSB configuration alarm usually mean?
It usually means the connected amplifier type, amplifier quantity, or communication state does not match the FSSB configuration expected by the CNC.
Are these alarms always caused by a bad amplifier?
Not always. Many of these alarms are caused by incorrect settings, axis assignment problems, optical cable issues, parameter mismatch, initialization failure, or a wrong hardware/software combination.
What should be checked after amplifier replacement?
Typical checks include amplifier type compatibility, FSSB recognition, axis assignment, parameter consistency, tandem settings, initialization behavior, and whether the control software matches the installed hardware.
What does illegal axis assignment mean on FANUC?
It means the servo axis number setting is incorrect, such as a negative value, duplicate value, or a value larger than the number of controlled axes in parameter (No.1023).
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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