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FANUC Alarm Code Guide

Find solutions to common Fanuc CNC alarm codes quickly and efficiently.

Servo Alarm
Spindle Alarm
System Alarm
Overtravel Alarm

FANUC Alarms: Quick Guide to Get Back Online​

When your FANUC CNC triggers an alarm, it's trying to tell you something. From simple overtravel to complex servo issues, these codes pinpoint where the problem lies.Our guide cuts through the complexity. We explain the most common alarms—what they mean, why they happen, and how to fix them. Whether you're facing alarm 401 or a stuck overtravel limit, you'll find clear, step-by-step solutions to minimize downtime.​​ You will learn how to:​​

  • Decode any FANUC alarm number.
  • Diagnose faults in servos, spindles, or system memory.
  • Perform basic checks before calling a technician.
  • Identify components that may need adjustment or replacement.

Get the knowledge to solve problems faster and keep your machines running.
FANUC SP9002 Alarm: Excessive Spindle Speed Deviation
The FANUC SP9002 alarm indicates an excessive spindle speed deviation. The related amplifier alarm number is 02. This alarm occurs when the detected spindle motor speed cannot follow the commanded spindle speed. In normal operation, the spindle motor feedback speed should closely follow the spindle command speed. If the detected speed is far away from the command speed, the CNC system may judge that the spindle cannot accelerate, decelerate, or rotate as required, and then generate the SP9002 alarm. SP9002 may be caused by excessive cutting load, unreasonable acceleration/deceleration time... Read more...
FANUC SP9001 Alarm: Spindle Motor Overheating
The FANUC SP9001 alarm indicates a spindle motor overheating alarm. The related amplifier alarm number is 01. This alarm occurs when the spindle software detects that the internal temperature of the spindle motor has exceeded the specified temperature range. When SP9001 occurs, the first step is to confirm whether the spindle motor is truly overheating or whether the temperature detection circuit is reporting an incorrect value. This can be checked by comparing the temperature shown in diagnosis No.403 with the actual motor temperature measured by an infrared thermometer or confirmed... Read more...
FANUC SV0468 Alarm: High-Speed HRV Setting Error for Amplifier
The FANUC SV0468 alarm indicates a high-speed HRV setting error for the amplifier. This alarm occurs when high-speed HRV control is enabled for an amplifier-controlled axis that does not support that HRV control level. HRV control is related to servo response and control performance. In a FANUC servo system, the available HRV level depends on the servo motor model, servo amplifier model, order specification, and supported control configuration. If the current HRV setting is higher than the capability of the installed motor or amplifier, the CNC system may generate the... Read more...
FANUC SV0466 Alarm: Motor and Amplifier Combination Mismatch
The FANUC SV0466 alarm indicates a motor and amplifier combination mismatch. This alarm occurs when the CNC system detects that the maximum current value of the servo amplifier does not match the maximum current value of the servo motor. In a FANUC servo system, the motor model, servo amplifier model, motor code, FSSB connection order, and servo parameters must match the actual machine configuration. If a drive has been replaced, a fourth axis has been added, a full machine parameter backup has been restored, or the motor code has been... Read more...
FANUC SV0465 Alarm: Failed to Read Amplifier ID Data
The FANUC SV0465 alarm indicates that the CNC system failed to read the amplifier ID data. This alarm occurs when the system cannot read the ID information from the servo amplifier at power-on. Inside the servo amplifier, there is a data chip that stores amplifier ID information. When the CNC system is powered on, it reads this ID information to identify the connected amplifier. If the ID data cannot be read correctly, the system may generate the SV0465 alarm immediately. This alarm is usually related to poor contact of the... Read more...
FANUC SV0463 Alarm: Slave Data Transmission Error
The FANUC SV0463 alarm indicates a slave data transmission error. This alarm occurs when the servo software side cannot receive correct data because of an FSSB communication error. FSSB, also known as Fanuc Serial Servo Bus, is the communication system between the CNC control unit and the servo amplifier system. If the FSSB parameters are not set correctly, the optical fiber cable is damaged, the cable is connected incorrectly, or the amplifier control board has poor contact, the servo software may not receive valid data and the CNC system may... Read more...
FANUC SV0462 Alarm: CNC Data Transmission Error
The FANUC SV0462 alarm indicates a CNC data transmission error. This alarm occurs when the amplifier cannot receive correct data from the control unit because of an FSSB communication error. FSSB, also known as Fanuc Serial Servo Bus, is used for communication between the CNC control unit and the servo amplifier system. If the FSSB optical fiber cable is damaged, loose, disconnected, connected incorrectly, or if the amplifier control board has poor contact, the data sent from the CNC may not be received correctly by the drive side. In this... Read more...
FANUC SV0460 Alarm: FSSB Communication Disconnected
The FANUC SV0460 alarm indicates an FSSB communication disconnected condition. This alarm occurs when the CNC system detects that FSSB communication has been interrupted or disconnected. FSSB, also known as Fanuc Serial Servo Bus, is the communication path between the CNC and servo amplifier system. If the optical fiber cable is loose, damaged, disconnected, or if an amplifier loses control power, the CNC may lose communication with the drive system and generate the SV0460 alarm. SV0460 is not always caused by a broken FSSB cable itself. In some cases, it... Read more...
FANUC SV0449 Alarm: Inverter IPM Alarm
The FANUC SV0449 alarm indicates an inverter IPM alarm. This alarm occurs when the servo amplifier IPM, also called the Intelligent Power Module, detects an abnormal condition. The IPM is an important power module inside the servo amplifier. It controls the power output to the servo motor and monitors abnormal current, short circuit, power module fault, and related drive conditions. If the IPM detects an abnormal condition, the CNC system may generate the SV0449 alarm. In many cases, SV0449 is caused by a motor short circuit, motor power cable ground... Read more...
FANUC SV0448 Alarm: Feedback Mismatch
The FANUC SV0448 alarm indicates a feedback mismatch alarm. This alarm occurs when the sign of the feedback data from the built-in pulse encoder is opposite to the sign of the feedback data from the external detector. SV0448 is usually related to a full-closed loop control system. In this type of system, the CNC uses both the servo motor built-in pulse encoder and an external detector, such as a linear scale or external encoder, to monitor axis movement. The feedback direction from both devices must be consistent. If the built-in... Read more...
FANUC SV0447 Alarm: Hard Disconnection External Detector
The FANUC SV0447 alarm indicates a hard disconnection alarm for the external detector. This alarm occurs when hardware detects a disconnection in the external detector feedback circuit. SV0447 usually occurs in a full-closed loop system, where the CNC system uses an external detector such as a linear scale, external encoder, or rotary encoder to detect the actual machine position. If the external detector signal is interrupted, the feedback cable is disconnected, the connector is loose, or the detector itself is faulty, the CNC system may generate the SV0447 alarm. Unlike... Read more...
FANUC SV0446 Alarm: Hard Disconnection Alarm
The FANUC SV0446 alarm indicates a hard disconnection alarm. This alarm occurs when hardware detects a disconnection in the built-in pulse encoder. The built-in pulse encoder is used to send motor feedback signals to the servo system. If the encoder feedback signal is interrupted, the encoder connector is loose, the motor feedback cable is damaged, or the encoder itself is faulty, the CNC system may generate the SV0446 alarm. Unlike SV0445, which is detected by digital servo software as a soft disconnection alarm, SV0446 is detected by hardware. Therefore, troubleshooting... Read more...

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