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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 PS0206 Alarm: Cannot Change Plane During Rigid Tapping
FANUC PS0206 means that the program attempted to change the selected plane or drilling axis while rigid-tapping mode was active. On an applicable M-series control, this commonly occurs when G17, G18, or G19 changes the working plane before the rigid-tapping canned cycle has been canceled. The official corrective direction is to modify the NC program. Keep one plane and one drilling axis throughout the active rigid-tapping cycle. If another plane is required, cancel the current cycle with the machine-approved canned-cycle cancellation command—normally G80—select the new plane, position the tool safely,... Read more...
FANUC PS0205 Alarm: Rigid Mode DI Signal Off
FANUC PS0205 means that the CNC reached a rigid-tapping cycle but did not receive the required rigid-mode confirmation DI signal from the PMC. On the FANUC systems covered by the newer alarm documentation, this confirmation is identified as RGTAP <G061.0>. If it is not ON when the CNC executes the applicable G84 or G74 block, the CNC stops with PS0205 / RIGID MODE DI SIGNAL OFF. The primary fault area is the machine-tool builder's PMC sequence and its rigid-tapping signal handling. On a multi-spindle or multi-path machine, incorrect spindle selection,... Read more...
FANUC PS0204 Alarm: Illegal Axis Operation in Rigid Tapping
FANUC PS0204 means that an illegal axis movement was commanded in the rigid-tapping sequence. The standard FANUC alarm description states that an axis movement was specified between the rigid-mode M-code block—commonly M29 Sxxxx—and the G84 or G74 tapping-cycle block. Correct the program so that all required positioning is completed before the rigid-mode command and no separate axis-movement block interrupts the sequence. On controls that use M29, the normal structure is: G00 X50.0 Y30.0 Z5.0 M29 S500 G84 Z-20.0 R2.0 F1.25 PS0204 is primarily a program-sequence alarm. It does not, by... Read more...
FANUC PS0203 Alarm: Rigid Tapping Command Error and Troubleshooting
FANUC PS0203 means that the rigid-tapping M code—commonly M29—or the associated S spindle-speed command is positioned incorrectly in the program. On a FANUC control that requires a rigid-mode M code, the usual correction is to command the approved rigid M code and spindle speed together, for example M29 S1000, and then execute the G84 or G74 tapping cycle without inserting another S command or an axis movement between them. PS0203 is a program or configuration alarm. The first step is to inspect the blocks immediately before the tapping cycle. Do... Read more...
FANUC PS0202 Alarm: Position LSI Overflow During Rigid Tapping
FANUC PS0202 means that the spindle distribution amount calculated during rigid tapping exceeded the internal limit of the CNC. FANUC alarm lists describe this condition as “spindle distribution value is too large” and identify it as a system error. On applicable FANUC 0i-F machining-center systems, spindle distribution can be viewed in diagnosis data No. 451. The documented maximum for a serial spindle is 32,767 pulses per 8 ms. The distribution amount changes with the rigid-tapping S command and the position-coder or rigid-tapping gear-ratio settings. If the calculated amount exceeds the... Read more...
FANUC PS0201 Alarm: Feedrate Not Found in Rigid Tap and Troubleshooting
FANUC PS0201 means that the CNC does not have a usable cutting feedrate for the rigid-tapping operation. The basic FANUC alarm description is that the required F command was not input. Depending on the CNC series and software, PS0201 can also be generated when the active F value is zero, is extremely small relative to the S command, or exceeds the permitted cutting-feed range. The first correction is therefore to inspect the tapping program—not the spindle amplifier. Confirm that a valid F value is active and that it matches the... Read more...
FANUC PS0200 Alarm: Illegal S Code Command in Rigid Tapping
FANUC PS0200 means that the S command used for rigid tapping is missing, outside the permitted range, or higher than the maximum spindle speed allowed for the selected gear. On the FANUC Series 0i-D / 0i Mate-D covered by the cited manuals, the relevant rigid-tapping speed limits are set by parameters 5241–5243, with parameter 5244 available for a fourth gear in applicable configurations. The first action should be to confirm the programmed S value and the gear actually selected by the machine. Do not immediately increase a parameter merely to... Read more...
FANUC SP9042 Alarm 42: No Position Coder One-Rotation Signal and Troubleshooting
FANUC SP9042 means that the spindle amplifier did not detect the position coder's one-rotation signal. The CNC typically displays SP9042 / SSPA:42, while the spindle amplifier displays alarm 42. FANUC Maintenance Manual B-65285EN describes alarm 42 as a condition in which the one-rotation signal of the position coder is not generated. The official troubleshooting direction is to verify the detector parameters, check the one-rotation signal at the approved test point, inspect or replace the connection cable and position coder, and test the spindle amplifier only after the feedback path has... Read more...
FANUC SP9034 Alarm 34: Illegal Spindle Parameter and Troubleshooting
FANUC SP9034 means that the spindle amplifier detected parameter data outside the range that can be specified. The CNC displays SP9034 / SSPA:34 ILLEGAL PARAMETER, while the spindle amplifier displays alarm 34. The correct action is to identify the invalid internal parameter number, map it to the applicable CNC spindle parameter, and restore the correct value from the exact motor parameter list or approved machine backup. On supported configurations, CNC diagnosis 720 provides the internal number. A value of 0 has a separate meaning: the motor model code used for... Read more...
FANUC SP9041 Alarm 41: Position Coder One-Rotation Signal Error and Troubleshooting
FANUC SP9041 means that the spindle amplifier detected the one-rotation signal from the position coder at an incorrect position. The CNC typically displays SP9041 / SSPA:41, while the spindle amplifier displays alarm 41. FANUC Maintenance Manual B-65285EN/04 describes alarm 41 as an incorrect generation position of the αi position coder one-rotation signal. The official procedure directs technicians to check the position-coder parameters, observe the coder Z signal, inspect cable shielding and routing, and finally test the spindle amplifier or its control board. Alarm location Typical display Meaning CNC SP9041 /... Read more...
FANUC SP9037 Alarm 37: Speed Detector Setting Error and Troubleshooting
FANUC SP9037 means that the spindle amplifier detected an incorrect parameter setting for the spindle motor speed detector. The CNC typically displays SP9037 / SSPA:37 ILLEGAL SETTING VELOCITY DETECTOR, while the spindle amplifier displays alarm 37. The CNC alarm list describes the direct cause as an incorrect setting for the number of pulses in the speed detector. FANUC's detailed αi spindle-amplifier maintenance procedure explains the related detection behavior: after an emergency-stop signal is input, the motor may fail to decelerate correctly or may accelerate; alarm 37 can also be issued... Read more...
FANUC SP9036 Alarm 36: Error Counter Overflow and Troubleshooting
FANUC SP9036 means that the spindle amplifier position error counter overflowed. The CNC displays SP9036 / SSPA:36 OVERFLOW ERROR COUNTER, while the spindle amplifier displays alarm 36. FANUC's detailed spindle-amplifier maintenance procedure identifies two main causes: an excessively large or incorrect spindle-to-motor gear-ratio setting, and an incorrect position-gain setting for the active position-control mode. A sequence problem can also cause the alarm if spindle motor excitation is removed by turning off SFR/SRV while the spindle remains in a position-control mode. Alarm location Typical display Meaning CNC SP9036 / SSPA:36 OVERFLOW... Read more...

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