Digitax HD M753 EtherCAT Drive Fault Codes (2026)

Categories: Drives, PLC & HMI, Faults & Alarm

Digitax HD M753 EtherCAT Drive Fault Codes (2026) – Troubleshooting guide for the Nidec Digitax HD M753 EtherCAT servo drive. Learn to interpret mnemonic trips, troubleshoot EtherCAT state errors, and use Connect software.

The Nidec Control Techniques Digitax HD M753 is a high-performance servo drive featuring onboard EtherCAT connectivity. Designed for decentralized motion control, it is a staple in high-speed synchronized machinery using Beckhoff, Omron, or other EtherCAT masters. When the M753 identifies an error, it stops the motor and displays a mnemonic trip code—such as OI.AC (Overcurrent) or Enc1 (Encoder 1 Fault).

This 2026 guide provides the diagnostic framework specifically for the M753, focusing on both hardware trips and EtherCAT communication status errors to help you restore high-precision motion synchronization.

Digitax HD M753 Fault Codes Reference Table

Below is the complete reference list of faults for the Digitax HD M753. Since this drive is integrated into EtherCAT networks, many trips may be related to synchronization timing (Sync Manager) or position loop deviations.

Fault Code and MeaningCause and Remedy
217

App Menu Changed
Cause:

The customization table for an application menu has changed. The menu that has been changed can be identified by the sub-trip number.



Remedy:


  • Reset the trip and perform a parameter save to accept the new settings.
11

Autotune 1
Cause:

Position feedback did not change or required speed could not be reached. The drive has tripped during an autotune.



Remedy:


  • Ensure the motor is free to turn i.e. mechanical brake was released.

  • Ensure Pr 03.026 and Pr 03.038 are set correctly (or appropriate 2nd motor map parameters).

  • Check feedback device wiring is correct.

  • Check encoder mechanical coupling to the motor.
12

Autotune 2
Cause:

Position feedback direction incorrect. The drive has tripped during a rotating autotune.



Remedy:


  • Check motor cable wiring is correct.

  • Check feedback device wiring is correct.

  • Swap any two motor phases.
13

Autotune 3
Cause:

Measured inertia has exceeded the parameter range or commutation signals changed in wrong direction. The drive has tripped during a rotating autotune or mechanical load measurement test.



Remedy:


  • Check motor cable wiring is correct.

  • Check feedback device U,V and W commutation signal wiring is correct.

  • Increase the test level.

  • If the test was carried out at standstill repeat the test with the motor rotating within the recommended speed range.
14

Autotune 4
Cause:

Drive encoder U commutation signal fail. The U commutation signal did not change during a rotating autotune.



Remedy:


  • Check feedback device U commutation signal wiring is correct (Encoder terminals 7 and 8).
15

Autotune 5
Cause:

Drive encoder V commutation signal fail. The V commutation signal did not change during a rotating autotune.



Remedy:


  • Check feedback device V commutation signal wiring is correct (Encoder terminals 9 and 10).
16

Autotune 6
Cause:

Drive encoder W commutation signal fail. The W commutation signal did not change during a rotating autotune.



Remedy:


  • Check feedback device W commutation signal wiring is correct (Encoder terminals 11 and 12).
17

Autotune 7
Cause:

Motor number of poles / position feedback resolution set incorrectly. The motor poles or the position feedback resolution have been set up incorrectly where position feedback is being used.



Remedy:


  • Check line per revolution for feedback device.

  • Check the number of poles in Pr 05.011.
18

Autotune Stopped
Cause:

Autotune test stopped before completion. The drive was prevented from completing an autotune test, because either the drive enable or the drive run were removed.



Remedy:


  • Check the drive enable signal (terminal 2 & 6) were active during the autotune.

  • Check the run command was active in Pr 08.005 during autotune.
19

Brake R Too Hot
Cause:

Braking resistor overload timed out (I2t). The Brake R Too Hot indicates that braking resistor overload has timed out. Initiated when Braking Resistor Thermal Accumulator (10.039) reaches 100%.



Remedy:


  • Ensure the values entered in Pr 10.030, Pr 10.031 and Pr 10.061 are correct.

  • If an external thermal protection device is being used and the braking resistor software overload protection is not required, set Pr 10.030, Pr 10.031 or Pr 10.061 to 0 to disable the trip.
99

CAM
Cause:

Advanced motion controller CAM failure. The CAM trip indicates that the advanced motion controller CAM has detected a problem (e.g. Start Index > Size, Table Index error, rate of change exceeded).



Remedy:


  • Check advanced motion controller CAM settings.

  • Evaluate sub-trip parameter definitions.
185

Card Access
Cause:

SD Card Write fail. The drive was unable to access the SD Card. File being written may be corrupted or data transfer incomplete.



Remedy:


  • Check SD Card is installed / located correctly.

  • Replace the SD Card.
177

Card Boot
Cause:

The Menu 0 parameter modification cannot be saved to the SD Card. Pr 11.042 set to Auto/Boot but necessary boot file not created.



Remedy:


  • Ensure that Pr 11.042 is correctly set, and then reset the drive to create the necessary file on the SD Card.

  • Re-attempt the parameter write to the Menu 0 parameter.
178

Card Busy
Cause:

SD Card cannot be accessed as it is being accessed by an option module.



Remedy:


  • Wait for the option module to finish accessing the SD Card and re-attempt the required function.
188

Card Compare
Cause:

SD Card file/data is different to the one in the drive. A Card Compare trip is initiated if the parameters on the SD Card are different to the drive.



Remedy:


  • Set Pr mm.000 to 0 and reset the trip.

  • Check to ensure the correct data block on the SD Card has been used for the compare.
179

Card Data Exists
Cause:

SD Card data location already contains data. An attempt has been made to store data on an SD Card in a data block which already contains data.



Remedy:


  • Erase the data in data location.

  • Write data to an alternative data location.
187

Card Drive Mode
Cause:

SD Card parameter set not compatible with current drive mode. The drive mode in the data block on the SD Card is different from the current drive mode.



Remedy:


  • Ensure the destination drive supports the drive operating mode in the parameter file.

  • Clear the value in Pr mm.000 and reset the drive.

  • Ensure destination drive operating mode is the same as the source parameter file.
182

Card Error
Cause:

SD Card data structure error. An error has been detected in the data structure on the card (folder structure missing, corrupt file, or duplicate IDs).



Remedy:


  • Erase all the data blocks and re-attempt the process.

  • Ensure the card is located correctly.

  • Replace the SD Card.
184

Card Full
Cause:

SD Card full. An attempt has been made to create a data block but there is not enough space.



Remedy:


  • Delete a data block or the entire SD Card to create space.

  • Use a different SD Card.
183

Card No Data
Cause:

SD Card data not found. An attempt has been made to access non-existent file or block.



Remedy:


  • Ensure data block number is correct.
180

Card Option
Cause:

Option modules installed are different between source drive and destination drive.



Remedy:


  • Ensure the correct option modules are installed.

  • Ensure the option modules are in the same option module slot as the parameter set stored.

  • Press the red reset button to acknowledge that the parameters for one or more of the option modules installed will be at their default values.

  • This trip can be suppressed by setting Pr mm.000 to 9666 and resetting the drive.
175

Card Product
Cause:

SD Card data blocks are not compatible with the drive derivative (Drive Derivative or Product Type different).



Remedy:


  • Use a different SD Card.

  • This trip can be suppressed by setting Pr mm.000 to 9666 and resetting the drive.
186

Card Rating
Cause:

The voltage and / or current rating of the source and destination drives are different.



Remedy:


  • Reset the drive to clear the trip.

  • Ensure that the drive rating dependent parameters have transferred correctly.

  • This trip can be suppressed by setting Pr mm.000 to 9666 and resetting the drive.
181

Card Read Only
Cause:

SD Card has the Read Only bit set.



Remedy:


  • Clear the read only flag by setting Pr mm.000 to 9777 and reset the drive. This will clear the read-only flag for all data blocks in the SD Card.
174

Card Slot
Cause:

Option module application program transfer has failed. Option module did not respond correctly.



Remedy:


  • Ensure the source / destination option module is installed on the correct slot.
35

Control Word
Cause:

Trip initiated from the Control Word (06.042) by setting bit 12.



Remedy:


  • Check the value of Pr 06.042.

  • Disable the control word in Control Word Enable (Pr 06.043).

  • When the control word is enabled, the trip can only be cleared by setting bit 12 to zero.
225

Current Offset
Cause:

Current feedback offset error. The current feedback offset is too large to be trimmed correctly.



Remedy:


  • Ensure that there is no possibility of current flowing in the output phases of the drive when the drive is not enabled.

  • Hardware fault – Contact the supplier of the drive.
97

Data Changing
Cause:

Drive parameters are being changed. A user action or a file system write is active that is changing the drive parameters and the drive has been commanded to enable.



Remedy:


  • Ensure the drive is not enabled when one of the following is being carried out: Loading defaults, Changing drive mode, Transferring data from SD Card or position feedback device, Transferring user programs.
247

Derivative identification error
Cause: There is a problem with the identifier associated with derivative image which customizes the drive.

Sub-trip reasons:

  • 1: There should be a derivative image in the product but this has been erased.

  • 2: The identifier is out of range.

  • 3: The derivative image has been changed.




Remedy:



  • Contact the supplier of the drive.
248

Derivative Image error
Cause: An error has been detected in the derivative image.

Sub-trip reasons:

  • 1 to 52: An error has been detected in the derivative image.

  • 61: The option module fitted in slot 1 is not allowed with the derivative image.

  • 62: The option module fitted in slot 2 is not allowed with the derivative image.

  • 63: The option module fitted in slot 3 is not allowed with the derivative image.

  • 64: The option module fitted in slot 4 is not allowed with the derivative image.

  • 70: An option module that is required by the derivative image is not fitted in any slot.

  • 71: An option module specifically required to be fitted in slot 1 not present.

  • 72: An option module specifically required to be fitted in slot 2 not present.

  • 73: An option module specifically required to be fitted in slot 3 not present.

  • 80 to 81: An error has been detected in the derivative image.




Remedy:



  • Contact the supplier of the drive.
199

Destination parameter write conflict
Cause: Destination parameters of two or more functions (Menus 3, 7, 8, 9, 12 or 14) within the drive are writing to the same parameter.



Remedy:



  • Set Pr mm.000 to ‘Destinations’ or 12001 and check all visible parameters in all menus for parameter write conflicts.
224

Power stage recognition: Unrecognized drive size
Cause: The control PCB has not recognized the drive size of the power circuit to which it is connected.



Remedy:



  • Ensure the drive is programmed to the latest firmware version.

  • Hardware fault – return drive to supplier.
31

EEPROM Fail (Default parameters loaded)
Cause: Default parameters have been loaded. The exact cause is identified by the sub-trip number:


  • 1: The most significant digit of the internal parameter database version number has changed.

  • 2: The CRCs applied to the parameter data stored in internal non-volatile memory indicate that a valid set of parameters cannot be loaded.

  • 3: The drive mode restored from internal non-volatile memory is outside the allowed range.

  • 4: The drive derivative image has changed.

  • 5: The power stage hardware has changed.

  • 6: The internal I/O hardware has changed.

  • 7: The position feedback interface hardware has changed.

  • 8: The control board hardware has changed.

  • 9: The checksum on the non-parameter area of the EEPROM has failed.




Remedy:



  • Default the drive and perform a reset.

  • Allow sufficient time to perform a save before the supply to the drive is removed.

  • If the trip persists – return drive to supplier.
189

Encoder 1: Drive position feedback interface power supply overload
Cause: The drive encoder power supply has been overloaded (Terminals 13 & 14).



Remedy:



  • Check encoder power supply wiring.

  • Disable the termination resistors (Pr 03.039 set to 0) to reduce current consumption.

  • For 5 V encoders with long cables, select 8 V (Pr 03.036) and install a 5 V voltage regulator close to the encoder.

  • Check the encoder specification to confirm if it is compatible with the encoder port power supply current capability.

  • Replace the encoder.

  • Use an external power supply with higher current capability.
190

Encoder 2: Drive encoder (Feedback) wire break
Cause: Wire break detected on the 15 way D-type connector.

Sub-trip reasons:

  • 1: Drive position feedback interface 1 on any input.

  • 2: Drive position feedback interface 2 on any input.

  • 11: Drive position feedback interface 1 on the A channel.

  • 12: Drive position feedback interface 1 on the B channel.

  • 13: Drive position feedback interface 1 on the Z channel.




Remedy:



  • Ensure that the position feedback device type selected in Pr 03.038 is correct.

  • If wire break detection is not required, set Pr 03.040 = XXX0 to disable the Encoder 2 trip.

  • Check cable continuity.

  • Check wiring of feedback signals is correct.

  • Check encoder power supply is set correctly (Pr 03.036).

  • Replace encoder.
191

Encoder 3: Phase offset incorrect while running
Cause: Incorrect UVW phase angle detected while running (RFC-S mode only) or SINCOS phase error.

Sub-trip 1: Interface 1 | Sub-trip 2: Interface 2.



Remedy:



  • Check encoder shield connections.

  • Ensure the encoder cable is one uninterrupted cable.

  • Check the encoder signal for noise with an oscilloscope.

  • Check the integrity of the encoder mechanical mounting.

  • For a UVW servo encoder, ensure that the phase rotation of the UVW commutation signals is the same as the phase rotation of the motor.

  • For a SINCOS encoder, ensure that motor and incremental SINCOS connections are correct.

  • Repeat the offset measurement test.
192

Encoder 4: Feedback device comms failure
Cause: Encoder communications timed out or message transfer time is too long. Can also be caused by wire break.

Sub-trip 1: Interface 1 | Sub-trip 2: Interface 2.



Remedy:



  • Ensure the encoder power supply setting (Pr 03.036) is correct.

  • Complete encoder auto-configuration (Pr 03.041).

  • Check the encoder wiring.

  • Replace the feedback device.
193

Encoder 5: Checksum or CRC error
Cause: Checksum or CRC error, or the SSI encoder is not ready. Can also indicate a wire break to a comms based encoder.

Sub-trip 1: Interface 1 | Sub-trip 2: Interface 2.



Remedy:



  • Check the encoder cable shield connections.

  • Ensure the cable is one uninterrupted cable.

  • Check the encoder signal for noise with an oscilloscope.

  • Check the comms resolution setting (Pr 03.035).

  • If using a Hiperface, EnDat encoder carry out an encoder auto-configuration (Pr 03.041 = Enabled).

  • Replace the encoder.
194

Encoder 6: Encoder has indicated an error
Cause: Encoder indicated an error or power supply failed to an SSI encoder.

Sub-trip 1: Interface 1 | Sub-trip 2: Interface 2.



Remedy:



  • For SSI encoders, check the wiring and encoder power supply setting (Pr 03.036).

  • Replace the encoder / contact the supplier of the encoder.
195

Encoder 7: Set-up parameters for position feedback device have changed
Cause: The set-up parameters for position feedback device has changed.

Sub-trip 1: Interface 1 | Sub-trip 2: Interface 2.



Remedy:



  • Reset the trip and perform a save.

  • Ensure Pr 3.033 and Pr 03.035 are set correctly or carry out an encoder auto-configuration (Pr 03.041 = Enabled).
196

Encoder 8: Position feedback interface has timed out
Cause: Position feedback interface communications time exceeds 250 μs.

Sub-trip 1: Interface 1 | Sub-trip 2: Interface 2.



Remedy:



  • Ensure the encoder is connected correctly.

  • Ensure that the encoder is compatible.

  • Increase baud rate.
197

Encoder 9: Position feedback is selected from a option module slot which does not have a feedback option module installed
Cause: Position feedback source selected in Pr 03.026 (or Pr 21.021) is not valid.



Remedy:



  • Check the setting of Pr 03.026 (or Pr 21.021 if the second motor parameters have been enabled).

  • Ensure that the option slot selected in Pr 03.026 has a feedback option module installed.
162

Encoder 12: Encoder could not be identified during auto-configuration
Cause: The drive is communicating with the encoder but the encoder type is not recognized.

Sub-trip 1: Interface 1 | Sub-trip 2: Interface 2.



Remedy:



  • Enter the encoder setup parameters manually.

  • Check to see the encoder supports auto-configuration.
163

Encoder 13: Data read from the encoder is out of range during auto-configuration
Cause: Data read from the encoder was out of the range. The tens in the sub-trip number indicate the interface number.

Sub-trip reasons:

  • x1: Rotary lines per revolution error.

  • x2: Linear comms pitch error.

  • x3: Linear line pitch error.

  • x4: Rotary turns bits error.

  • x5: Communications bits error.

  • x6: Calculation time is too long.

  • x7: Line delay measured is longer than 5 μs.




Remedy:



  • Enter the encoder setup parameters manually.

  • Check to see the encoder supports auto-configuration.
6

External Trip
Cause: An External Trip has occurred. Can be initiated by writing 6 in Pr 10.038.

Sub-trip reasons:

  • 1: External Trip Mode (08.010) = 1 or 3 and Safe Torque Off input 1 is low.

  • 2: External Trip Mode (08.010) = 2 or 3 and Safe Torque Off input 2 is low.

  • 3: External Trip (10.032) = 1.




Remedy:



  • Check the Safe Torque Off signal voltage (on terminals 2 & 6) equals to 24 V.

  • Check the value of Pr 08.009 which indicates the digital state of terminals 2 & 6.

  • If external trip detection is not required, set Pr 08.010 to OFF (0).

  • Check the value of Pr 10.032. Select ‘Destinations’ in Pr mm.000 to find controlling parameters.

  • Ensure Pr 10.032 or Pr 10.038 (= 6) is not being controlled by serial comms.
HF01

Data processing error: CPU address error
Cause: A CPU address error has occurred. Control PCB failure.



Remedy:



  • Hardware fault – Contact the supplier of the drive.
HF02

Data processing error: DMAC address error
Cause: A DMAC address error has occurred. Control PCB failure.



Remedy:



  • Hardware fault – Contact the supplier of the drive.
HF03

Data processing error: Illegal instruction
Cause: An illegal instruction has occurred. Control PCB failure.



Remedy:



  • Hardware fault – Contact the supplier of the drive.
HF04

Data processing error: Illegal slot instruction
Cause: An illegal slot instruction has occurred. Control PCB failure.



Remedy:



  • Hardware fault – Contact the supplier of the drive.
HF05

Data processing error: Undefined exception
Cause: An undefined exception error has occurred. Control PCB failure.



Remedy:



  • Hardware fault – Contact the supplier of the drive.
HF06

Data processing error: Reserved exception
Cause: A reserved exception error has occurred. Control PCB failure.



Remedy:



  • Hardware fault – Contact the supplier of the drive.
HF07

Data processing error: Watchdog failure
Cause: A watchdog failure has occurred. Control PCB failure.



Remedy:



  • Hardware fault – Contact the supplier of the drive.
HF08

Data processing error: CPU Interrupt crash
Cause: A CPU interrupt crash has occurred. Control PCB failure.



Remedy:



  • Hardware fault – Contact the supplier of the drive.
HF09

Data processing error: Free store overflow
Cause: A free store overflow has occurred. This trip indicates that the control PCB on the drive has failed.



Remedy:



  • Hardware fault – Contact the supplier of the drive.
HF10

Data processing error: Parameter routing system error
Cause: A Parameter routing system error has occurred. This trip indicates that the control PCB on the drive has failed.



Remedy:



  • Hardware fault – Contact the supplier of the drive.
HF11

Data processing error: Access to EEPROM failed
Cause: Access to the drive EEPROM has failed. This trip indicates that the control PCB on the drive has failed.



Remedy:



  • Hardware fault – Contact the supplier of the drive.
HF12

Data processing error: Main program stack overflow
Cause: The main program stack overflow has occurred (Sub-trips: 1=Background, 2=Timed, 3=Interrupts). This trip indicates that the control PCB on the drive has failed.



Remedy:



  • Hardware fault – Contact the supplier of the drive.
HF13

Data processing error: Firmware incompatible with hardware
Cause: The drive firmware is not compatible with the hardware. The sub-trip number gives the actual ID code of the control board hardware.



Remedy:



  • Re-program the drive with the latest version of the drive firmware for Digitax HD M753.

  • Hardware fault – Contact the supplier of the drive.
HF14

Data processing error: CPU register bank error
Cause: A CPU register bank error has occurred. This trip indicates that the control PCB on the drive has failed.



Remedy:



  • Hardware fault – Contact the supplier of the drive.
HF15

Data processing error: CPU divide error
Cause: A CPU divide error has occurred. This trip indicates that the control PCB on the drive has failed.



Remedy:



  • Hardware fault – Contact the supplier of the drive.
HF16

Data processing error: RTOS error
Cause: A RTOS error has occurred. This trip indicates that the control PCB on the drive has failed.



Remedy:



  • Hardware fault – Contact the supplier of the drive.
HF17

Data processing error: Clock supplied to control board out of spec
Cause: The clock supplied to the control board logic is out of specification.



Remedy:



  • Hardware fault – Contact the supplier of the drive.
HF18

Data processing error: Internal flash memory has failed
Cause: Internal flash memory failed when writing option module parameter data. (Sub-trip 1: Programming error, 2: Erase setup menus failed, 3: Erase application menus failed).



Remedy:



  • Hardware fault – Contact the supplier of the drive.
HF19

Data processing error: CRC check on the firmware has failed
Cause: The CRC check on the drive firmware has failed.



Remedy:



  • Re-program the drive.

  • Hardware fault – Contact the supplier of the drive.
HF20

Data processing error: ASIC is not compatible with the hardware
Cause: The ASIC version is not compatible with the drive firmware.



Remedy:



  • Hardware fault – Contact the supplier of the drive.
HF23 to HF25

Hardware fault
Cause: Unspecified hardware fault.



Remedy:



  • If this trip occurs please consult the drive supplier.
Inductance (8)

Inductance measurement out of range or motor saturation not detected
Cause: Occurs in RFC-S mode. Motor inductances are not suitable for the operation, Ld/Lq ratio/difference is too small, or saturation characteristic cannot be measured.



Remedy:



  • Sub-trip 1 & 2: Ensure that RFC Low Speed Mode (05.064) is set to Non-salient (1), Current (2) or Current No test (3).

  • Sub-trip 3: None. The trip acts as a warning regarding position feedback phase angle or measured values.

  • Sub-trip 4: Stationary autotune is not possible. Perform a minimal movement or rotating autotune. Or use a position feedback device with commutation signals/absolute position.
I/O Overload (26)

Digital output overload
Cause: Total current drawn from 24 V user supply or digital output exceeded limit (>100mA).



Remedy:



  • Check total loads on digital outputs.

  • Check control wiring is correct.

  • Check output wiring is undamaged.
Keypad Mode (34)

Keypad removed while in keypad mode
Cause: Drive is in keypad mode and keypad has been removed or disconnected.



Remedy:



  • Re-install keypad and reset.

  • Change Reference Selector (01.014) to select the reference from another source.
Motor Too Hot (20)

Output current overload timed out (I2t)
Cause: Motor thermal overload based on Rated Current and Motor Thermal Time Constant. Drive trips when accumulator reaches 100%.



Remedy:



  • Ensure the load is not jammed / sticking.

  • Check the load on the motor has not changed.

  • If seen during auto-tune in RFC-S mode, ensure motor Rated Current is ≤ Heavy duty current rating of drive.

  • Tune the Rated Speed (RFC-A mode only).

  • Check feedback signal for noise.

  • Ensure motor rated current is not zero.

  • Can be disabled by setting thermal protection mode Pr 04.016 to 1.
Name Plate (176)

Electronic nameplate transfer has failed
Cause: Electronic name plate transfer between drive and motor failed (memory space, comms, or checksum).



Remedy:



  • Ensure encoder memory has at least 128 bytes (nameplate data) or 256 bytes (motor object).

  • Ensure option slot has a feedback option module installed.

  • Check if encoder has been initialized in Position Feedback Initialized (03.076).

  • Verify the encoder wiring.
OHt Brake (101)

Braking IGBT over-temperature
Cause: Braking IGBT over-temperature detected based on software thermal model.



Remedy:



  • Check braking resistor value is greater than or equal to the minimum resistance value.
OHt Control (23)

Control stage over temperature
Cause: Control stage over-temperature detected (Control board thermistor or I/O board thermistor).



Remedy:



  • Check enclosure / drive fans are still functioning correctly.

  • Check enclosure ventilation paths and door filters.

  • Increase ventilation.

  • Reduce the drive switching frequency.

  • Check ambient temperature.
OHt dc bus (27)

DC bus over temperature
Cause: DC bus component over temperature based on software thermal model.



Remedy:



  • Check the AC supply voltage balance and levels.

  • Check DC bus ripple level.

  • Reduce duty cycle or motor load.

  • Check output current stability. If unstable:

    • Check motor map settings (Pr 05.006 – 05.011).

    • Disable slip compensation or dynamic V to F operation.

    • Select fixed boost or high stability space vector modulation.

    • Disconnect load and complete rotating auto-tune.

    • Auto-tune rated speed value.

    • Reduce speed loop gains.

    • Add speed feedback or current demand filter.

    • Check encoder signals for noise.

    • Check encoder mechanical coupling.
OHt Inverter (21)

Inverter over temperature based on thermal model
Cause: IGBT junction over-temperature detected. Sub-trip 100: Inverter thermal model; Sub-trip 300: Braking IGBT thermal model.



Remedy:



  • Reduce the selected drive switching frequency.

  • Ensure Auto-switching Frequency Change Disable (05.035) is set to Off.

  • Reduce duty cycle or motor load.

  • Increase acceleration / deceleration rates.

  • Check DC bus ripple.

  • Ensure all three input phases are present and balanced.

  • For sub-trip 300: Reduce the braking load.
OHt dc bus (27)

DC bus over temperature
Cause:

A DC bus component over-temperature has been detected based on a software thermal model. This includes effects of output current and DC bus ripple.



Remedy:


  • Check the AC supply voltage balance and levels.

  • Check DC bus ripple level.

  • Reduce duty cycle.

  • Reduce motor load.

  • Check the output current stability.

  • Check motor map settings (Pr 05.006 – Pr 05.011).

  • Disable slip compensation (Pr 05.027 = 0).

  • Disconnect load and complete a rotating auto-tune.

  • Check encoder signals for noise.
OHt Inverter (21)

Inverter over temperature based on thermal model
Cause:

An IGBT junction over-temperature has been detected based on a software thermal model.



Remedy:


  • Reduce the selected drive switching frequency.

  • Ensure Auto-switching Frequency Change Disable (05.035) is set to Off.

  • Reduce duty cycle.

  • Increase acceleration / deceleration rates.

  • Reduce motor load.

  • Check DC bus ripple.

  • Ensure all three input phases are present and balanced.

  • Reduce the braking load (if sub-trip 300).
OHt Power (22)

Power stage over temperature
Cause:

A power stage over-temperature has been detected via thermistor measurement.



Remedy:


  • Check enclosure / drive fans are functioning correctly.

  • Force heatsink fans to run at maximum speed.

  • Check enclosure ventilation paths and door filters.

  • Increase ventilation.

  • Reduce drive switching frequency.

  • Reduce duty cycle.

  • Check derating tables to confirm drive sizing.
OI ac (3)

Instantaneous output over current detected
Cause:

The instantaneous drive output current has exceeded VM_DRIVE_CURRENT[MAX].



Remedy:


  • Acceleration/deceleration rate is too short.

  • If seen during auto-tune, reduce the voltage boost.

  • Check for short circuit on the output cabling.

  • Check integrity of the motor insulation using an insulation tester.

  • Check feedback device wiring and mechanical coupling.

  • Check feedback signals are free from noise.

  • Reduce values in speed loop gain parameters.
OI Brake (4)

Braking IGBT over current detected
Cause:

Over current detected in braking IGBT or braking IGBT protection has been activated (short circuit protection).



Remedy:


  • Check brake resistor wiring.

  • Check braking resistor value is greater than or equal to the minimum resistance value.

  • Check braking resistor insulation.
OI dc (109)

Power module over current detected from IGBT on state voltage monitoring
Cause:

Short circuit protection for the drive output stage has been activated.



Remedy:


  • Disconnect the motor cable at the drive end and check the motor and cable insulation with an insulation tester.

  • Replace the drive.
OI Snubber (92)

Snubber over-current detected
Cause:

An over-current condition has been detected in the rectifier snubber circuit.



Remedy:


  • Ensure the internal EMC Filter is installed.

  • Ensure motor cable length does not exceed maximum for selected switching frequency.

  • Check for supply voltage imbalance.

  • Check for supply disturbance such as notching from a DC drive.

  • Check motor and cable insulation.

  • Install an output line reactor.
Option Disable (215)

Option module does not acknowledge during drive mode changeover
Cause:

The option module did not acknowledge to the drive that communications with the drive has been stopped during mode changeover.



Remedy:


  • Reset the trip.

  • If the trip persists, replace the option module.
Out Phase Loss (98)

Output phase loss detected
Cause:

Phase loss has been detected at the drive output (U, V, or W phase disconnected).



Remedy:


  • Check motor and drive connections.

  • To disable the trip set Output Phase Loss Detection Enable (06.059) = 0.
Over Speed (7)

Motor speed has exceeded the over speed threshold
Cause:

The Output Frequency or Speed Feedback has exceeded the threshold set in Over Speed Threshold (03.008).



Remedy:


  • Check the motor is not being driven by another part of the system.

  • Reduce the Speed Controller Proportional Gain (03.010) to reduce overshoot.

  • If an SSI encoder is being used, set Pr 03.047 to 1.
Over Volts (2)

DC bus voltage has exceeded the peak or continuous level
Cause:

DC bus voltage exceeded VM_DC_VOLTAGE[MAX] or VM_DC_VOLTAGE_SET[MAX] for 15s.



Remedy:


  • Increase deceleration ramp (Pr 00.004).

  • Decrease the braking resistor value (staying above minimum).

  • Check nominal AC supply level.

  • Check for supply disturbances causing DC bus rise.

  • Check motor insulation.
Phase Loss (32)

Supply phase loss
Cause:

Input phase loss or large supply imbalance detected. Also detected by monitoring DC bus ripple.



Remedy:


  • Check the AC supply voltage balance and level at full load.

  • Check the DC bus ripple level with an isolated oscilloscope.

  • Check the output current stability.

  • Check for mechanical resonance with the load.

  • Reduce duty cycle or motor load.

  • Disable phase loss detection, set Pr 06.047 to 2.
Phasing Error (198)

RFC-S mode phasing failure due to incorrect phase angle
Cause:

Phase offset angle in Pr 03.025 is incorrect if position feedback is used.



Remedy:


  • Check encoder wiring and signals for noise.

  • Check encoder mechanical coupling.

  • Perform an auto-tune to measure encoder phase angle.

  • Ensure motor parameters are set correctly.

  • Reduce speed controller gains.
Power Comms (90)

Communication lost between power, control and rectifier modules
Cause:

Communications problem within the power system of the drive.



Remedy:


  • Hardware fault – Contact the supplier of the drive.
Power Data (220)

Power system configuration data error
Cause:

Error in the configuration data stored in the power system (e.g., CRC error, version mismatch).



Remedy:


  • Hardware fault – Contact the supplier of the drive.
Power Down Save (37)

Power down save error
Cause:

An error has been detected in the power down save parameters saved in non-volatile memory.



Remedy:


  • Perform a 1001 save in Pr mm.000 to ensure that the trip doesn’t occur the next time the drive is powered up.
PSU (5)

Internal power supply fault
Cause:

One or more internal power supply rails are outside limits or overloaded.



Remedy:


  • Remove any option modules and perform a reset.

  • Remove encoder connection and perform a reset.

  • Hardware fault within the drive – return the drive to the supplier.
PSU 24V (9)

24V internal power supply overload
Cause:

Total user load (digital outputs and encoder supply) has exceeded the internal 24V limit.



Remedy:


  • Reduce the load and reset.

  • Provide an external 24 V power supply on control terminal 2.

  • Remove all option modules.
Resistance (33)

Measured resistance has exceeded the parameter range
Cause:

Measured motor stator resistance is too high or an attempt to test failed. Maximum allowable resistance exceeded.



Remedy:


  • Check value entered in stator resistance matches allowed range.

  • Check motor cable connections.

  • Check integrity of motor stator winding.

  • Check motor phase to phase resistance at drive and motor terminals.

  • Select fixed boost mode (Pr 05.014 = Fixed).
216
Slot App Menu
Cause: More than one option slot has requested to customize the application menus 18, 19 and 20. The sub-trip number indicates which option slot has been allowed to customize the menus.



Remedy:

  • Ensure that only one of the Application modules is configured to customize the application menus 18, 19 and 20.
204, 209, 214
SlotX Different
Cause: The option module in option slot X on the drive is a different type to that installed when parameters were last saved on the drive. The sub-trip number gives the identification code of the module that was originally fitted.



Remedy:

  • Turn off the power, ensure the correct option modules are installed in the correct option slots and re-apply the power.

  • Confirm that the currently installed option module is correct, ensure option module parameters are set correctly and perform a user save in Pr mm.000.
202, 207, 212
SlotX Error
Cause: The option module in option slot X on the drive has detected an error. The reason for the error can be identified by the sub-trip number.



Remedy:

  • See the relevant Option Module User Guide for details of the trip.
200, 205, 210
SlotX HF
Cause: The option module in option slot X cannot operate. The possible causes of the trip can be identified by the sub-trip number (e.g., Module category unidentified, insufficient memory, etc.).



Remedy:

  • Ensure the option module is installed correctly.

  • Replace the option module.

  • Replace the drive.
203, 208, 213
SlotX Not Fitted
Cause: The option module in option slot X on the drive has been removed since the last power up.



Remedy:

  • Ensure the option module is installed correctly.

  • Re-install the option module.

  • To confirm that the removed option module is no longer required perform a save function in Pr mm.000.
201, 206, 211
SlotX Watchdog
Cause: The option module installed in Slot X has started the option watchdog function and then failed to service the watchdog correctly.



Remedy:

  • Replace the option module.
226
Soft Start
Cause: The soft start relay in the drive failed to close or the soft start monitoring circuit has failed.



Remedy:

  • Hardware fault – Contact the supplier of the drive.
221
Stored HF
Cause: A hardware trip (HF01 – HF20) has occurred and the drive has been power cycled. The sub-trip number identifies the HF trip i.e. stored HF.17.



Remedy:

  • Enter 1299 in Pr mm.000 and press reset to clear the trip.
227
Sub-array RAM
Cause: An option module, derivative image or user program image has requested more parameter RAM than is allowed. The RAM allocation is checked in order of resulting sub-trip numbers.



Remedy:

  • Check option module configuration.

  • Check user program image size.

  • Reduce parameter RAM usage.
218
Temp Feedback
Cause: An internal thermistor has failed. The thermistor location can be identified by the sub-trip number (e.g., Control PCB, Power module, Rectifier).



Remedy:

  • Hardware fault – Contact the supplier of the drive.
10
Th Brake Res
Cause: Brake resistor over temperature. Hardware based braking resistor thermal monitoring is connected and the resistor is overheating.



Remedy:

  • Check brake resistor wiring.

  • Check braking resistor value is greater than or equal to the minimum resistance value.

  • Check braking resistor insulation.
25
Th Short Circuit
Cause: Motor thermistor short circuit. The motor thermistor connected to the drive is short circuit or low impedance i.e. < 50 Ω.



Remedy:

  • Check thermistor continuity.

  • Replace motor / motor thermistor.
24
Thermistor
Cause: Motor thermistor over-temperature. The motor thermistor connected to the drive has indicated a motor over temperature.



Remedy:

  • Check motor temperature.

  • Check P1 Thermistor Trip Threshold (03.120).

  • Check thermistor continuity.
110
Undefined
Cause: The drive has tripped and the cause of the trip is Undefined. The power system has generated a trip but did not identify it.



Remedy:

  • Hardware fault – return the drive to the supplier.
249
User Program
Cause: Onboard user program error. An error has been detected in the onboard user program image. The reason can be identified by the sub-trip number (e.g., Divide by zero, Array bounds violation, Invalid ID code).



Remedy:

  • Check the user program code and logic.

  • Review sub-trip codes (1-208) in the manual for specific debugging details.

  • Ensure image compatibility with control board.
96
User Prog Trip
Cause: Trip generated by an onboard user program using a function call which defines the sub-trip number.



Remedy:

  • Check the user program.
36
User Save
Cause: User Save error / not completed. An error has been detected in the user save parameters saved in non-volatile memory (e.g. power removed during save).



Remedy:

  • Perform a user save in Pr mm.000 to ensure that the trip doesn’t occur the next time the drive is powered up.

  • Ensure that the drive has enough time to complete the save before removing the power to the drive.
40-89, 112-159
User Trip
Cause: User generated trip. These trips are not generated by the drive and are to be used by the user to trip the drive through an application program.



Remedy:

  • Check the user program.
30
Watchdog
Cause: Control word watchdog has timed out. The control word has been enabled and has timed out.



Remedy:

  • Once Pr 06.042 bit 14 has been changed from 0 to 1 to enable the watchdog, this must be repeated every 1 s or a Watchdog trip will be initiated.

  • The watchdog is disabled when the trip occurs and must be re-enabled if required when the trip is reset.
Error 1

Programming Error
Cause: There is not enough drive memory requested by all the option modules.


Remedy:

Power down drive and remove some of the option modules until the message disappears.
Error 2

Programming Error
Cause: At least one option module did not acknowledge the reset request.


Remedy:

Power cycle drive.
Error 3

Programming Error
Cause: The boot loader failed to erase the processor flash.


Remedy:

Power cycle drive and try again. If problem persists, return drive.
Error 4

Programming Error
Cause: The boot loader failed to program the processor flash.


Remedy:

Power cycle drive and try again. If problem persists, return drive.
Error 5

Programming Error
Cause: One option module did not initialize correctly. Option module did not set Ready to Run flag.


Remedy:

Remove faulty option module.
Brake Resistor

Brake resistor overload
Cause: Braking Resistor Thermal Accumulator (10.039) in the drive has reached 75.0 % of the value at which the drive will trip.


Remedy:

Check braking resistor sizing and application load.
Motor Overload

Motor Protection Accumulator High
Cause: Motor Protection Accumulator (04.019) in the drive has reached 75.0 % of the value at which the drive will trip and the load on the drive is > 100 %.


Remedy:

Reduce motor load or check motor rating parameters.
Ind Overload

Regen inductor overload
Cause: Inductor Protection Accumulator (04.019) in the drive has reached 75.0 % of the value at which the drive will trip and the load on the drive is > 100 %.


Remedy:

Check regen inductor sizing and load conditions.
Drive Overload

Drive over temperature
Cause: Percentage Of Drive Thermal Trip Level (07.036) in the drive is greater than 90 %.


Remedy:

Check drive cooling, ambient temperature, and load.
Auto Tune

Autotune active
Cause: The autotune procedure has been initialized and an autotune in progress.


Remedy:

Wait for autotune to complete.
Limit Switch

Limit switch active
Cause: Indicates that a limit switch is active and that is causing the motor to be stopped.


Remedy:

Check system limit switches and machine position.

How to Read M753 Faults via Connect & EtherCAT Masters

In 2026, the M753 is typically managed via an EtherCAT master. Troubleshooting involves both the drive’s local diagnostics and the network’s state machine.

  • Connect Software (via USB or Ethernet): Use Nidec’s Connect software to access the drive’s internal parameters. The Trip Log (Menu 10) stores the last 10 trips with microsecond data-logging, allowing you to see exactly what the torque and speed were when the network lost sync.
  • EtherCAT State Machine: If the drive is not tripping but won’t run, check the EtherCAT status LED. The drive must transition through Init, Pre-Op, Safe-Op to reach Op (Operational). Errors in this transition are often logged in Menu 17 (EtherCAT specific parameters).
  • Sub-trip Mnemonic: Parameter 10.070 displays a sub-trip string. This is essential for hardware-related trips as it identifies which specific internal module or encoder channel caused the shutdown.
  • Distributed Clocks (DC): If you encounter Sync or AL Status errors, use your EtherCAT master’s diagnostic tool (e.g., TwinCAT) to verify the Distributed Clock synchronization between the master and the M753.

Frequently Asked Questions (FAQ)

Q: What is the difference between a Trip and a Warning on the M753?

A: A Trip (Solid code) is a protective shutdown that stops the motor immediately to protect the drive or the mechanical system. A Warning (Flashing code) indicates a “near-trip” condition, such as Hot (Heatsink temperature) or O.Ld (Load Warning), which allows the PLC to reduce the cycle speed before a hard stop occurs.

Q: How do I reset a Digitax HD M753 fault?

A: Once the cause is cleared, you can reset the drive via:

  • Pressing the Red STOP/RESET button on the drive keypad (if installed).
  • Cycling the Main Power (Wait for the display to go completely dark before reapplying power).
  • Sending a Fault Reset command via the EtherCAT Control Word (Bit 7).
  • Toggling a Digital Input assigned to the “Reset” function (Parameter 10.033).

Q: What does “inh” (Inhibit) mean?

A: “inh” is not a fault. It is a status code indicating that the Safe Torque Off (STO) terminals (Dual channel) are not receiving a 24V signal. The drive is healthy but prevented from running by an external safety circuit or E-stop. In EtherCAT systems, “inh” will prevent the drive from entering the “Op” state.

Q: Where is the fault history stored?

A: The trip history is stored in non-volatile memory in Menu 10. Even if the drive is powered down, the last 10 trips are retained. The most recent trip code is always found in Parameter 10.020.

Q: My drive shows “Enc1,” what does that mean in a servo system?

A: This is a Primary Encoder Fault. It means the drive has lost position feedback. Check the motor encoder cable for damage, ensure the shield is properly grounded, and verify that the encoder connectors are fully seated at both the motor and drive ends.