Digitax ST Drive Fault Codes (2026)

Categories: Drives, PLC & HMI, Faults & Alarm

Digitax ST Drive Fault Codes (2026) – Comprehensive 2026 troubleshooting guide for the Nidec Control Techniques Digitax ST servo drive. Learn to interpret mnemonic trips like OI.AC, Enc1, and HF hardware faults.

The Nidec Control Techniques Digitax ST is a high-dynamic response servo drive designed for pulse-duty applications requiring high peak torque and rapid acceleration. Although now part of a mature product line, it remains widely used in 2026 for indexing, pick-and-place, and synchronized motion systems. When the drive identifies a problem, it stops the motor and displays a mnemonic trip code—an abbreviated English string such as OI.AC (Overcurrent) or Enc1 (Encoder 1 Fault).

This guide provides the diagnostic framework to help you interpret these codes, manage the drive’s two SM-option slots, and resolve trips to maintain high-precision motion timing.

Digitax ST Fault Codes Reference Table

Below is the reference list of trips for the Digitax ST. Because this is a servo drive, many trips are related to position feedback and high-speed current loop stability. Please locate the code appearing on your drive’s LED display.

Fault Code and MeaningCause and Remedy
OI.AC / 3

Instantaneous output over current detected
Cause:

Over current threshold exceeded (Kc/0.45). Acceleration/deceleration rate is too short.



Remedy:


  • If seen during autotune reduce voltage boost Pr 5.15.

  • Check for short circuit on output cabling.

  • Check integrity of motor insulation.

  • Check feedback device wiring.

  • Check feedback device mechanical coupling.

  • Check feedback signals are free from noise.

  • Check if motor cable length is within limits.

  • Reduce the values in speed loop gain parameters (Pr 3.10, Pr 3.11, Pr 3.12).

  • Reduce the values in current loop gain parameters (Pr 4.13 and Pr 4.14).
br.th / 10

Braking resistor thermistor temperature monitoring fail
Cause:

Braking resistor issue or incorrect parameter setting.



Remedy:


  • If no brake resistor is installed, set Pr 0.51 (or Pr 10.37) to 8 to disable this trip.

  • Ensure that the braking resistor thermistor is connected correctly.

  • Ensure that the fan in the drive is working correctly.

  • Replace the braking resistor.
C.Acc / 185

SMARTCARD trip: Read / Write fail
Cause:

SMARTCARD is not writing data to data location 500 to 999.



Remedy:


  • Check SMARTCARD is installed / located correctly.

  • Replace SMARTCARD.
C.boot / 177

SMARTCARD trip: Menu 0 parameter modification not saved
Cause:

Necessary file not created on SMARTCARD. A write to menu 0 was initiated via keypad with Pr 11.42 set to auto(3) or boot(4).



Remedy:


  • Ensure that Pr 11.42 is correctly set and reset the drive to create the necessary file on the SMARTCARD.

  • Re-attempt the parameter write to the menu 0 parameter.
C.bUSY / 178

SMARTCARD trip: Card busy
Cause:

SMARTCARD cannot perform the required function as it is being accessed by a Solutions Module.



Remedy:

Wait for the Solutions Module to finish accessing the SMARTCARD and then re-attempt the required function.
C.Chg / 179

SMARTCARD trip: Data location already contains data
Cause:

Attempting to write to a location that is not empty.



Remedy:


  • Erase data in data location.

  • Write data to an alternative data location.
C.cPr / 188

SMARTCARD trip: Value mismatch
Cause:

The values stored in the drive and the values in the data block on the SMARTCARD are different.



Remedy:

Press the red reset button.
C.dAt / 183

SMARTCARD trip: Data location empty
Cause:

Data location specified does not contain any data.



Remedy:

Ensure data block number is correct.
C.Err / 182

SMARTCARD trip: Data is corrupted
Cause:

Corrupted data on card.



Remedy:


  • Ensure the card is located correctly.

  • Erase data and retry.

  • Replace SMARTCARD.
C.Full / 184

SMARTCARD trip: Card full
Cause:

No space left on SMARTCARD.



Remedy:

Delete a data block or use different SMARTCARD.
cL2 / 28

Analog input 2 current loss
Cause:

Current signal loss in current mode.



Remedy:

Check analog input 2 (terminal 7) current signal is present (4-20 mA, 20-4 mA).
cL3 / 29

Analog input 3 current loss
Cause:

Current signal loss in current mode.



Remedy:

Check analog input 3 (terminal 8) current signal is present (4-20 mA, 20-4 mA).
CL.bit / 35

Trip initiated from control word
Cause:

Trip initiated via Pr 6.42.



Remedy:

Disable the control word by setting Pr 6.43 to 0 or check setting of Pr 6.42.
C.OPtn / 180

SMARTCARD trip: Solutions Modules difference
Cause:

Solutions Modules installed are different between source drive and destination drive.



Remedy:


  • Ensure correct Solutions Modules are installed.

  • Ensure Solutions Modules are in the same Solutions Module slot.

  • Press the red reset button.
C.Prod / 175

SMARTCARD trip: Incompatible product
Cause:

The data blocks on the SMARTCARD are not compatible with this product.



Remedy:


  • Erase all data on the SMARTCARD by setting Pr xx.00 to 9999 and pressing the red reset button.

  • Replace SMARTCARD.
C.Rdo / 181

SMARTCARD trip: Read Only bit set
Cause:

Card is read-only.



Remedy:


  • Enter 9777 in Pr xx.00 to allow SMARTCARD Read / Write access.

  • Ensure card is not writing to data locations 500 to 999.
C.rtg / 186

SMARTCARD trip: Rating difference
Cause:

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



Remedy:

Press the red reset button. Note: Drive rating dependent parameters (RA coding) will not be transferred or will be set to default.
C.SLX / 172, 173, 174

Error transferring user program
Cause:

Error during transfer from Solutions Module to SMARTCARD (or vice versa).



Remedy:

See section 10.2.8 SM-Applications Modules And Motion Processors program to/from SMARTCARD transfer system.
C.TyP / 187

SMARTCARD trip: Parameter set not compatible
Cause:

SMARTCARD parameter set not compatible with drive.



Remedy:


  • Press the reset button.

  • Ensure destination drive type is the same as the source parameter file drive type.
dESt / 199

Parameter writing conflict
Cause:

Two or more parameters are writing to the same destination parameter.



Remedy:

Set Pr xx.00 = 12001 check all visible parameters in the menus for duplication.
EEF / 31

EEPROM data corrupted
Cause:

Serial comms will timeout with remote keypad on the drive RS485 comms port.



Remedy:

This trip can only be cleared by loading default parameters and saving parameters.
EnC1 / 189

Drive encoder trip: Power supply overload
Cause:

Encoder power supply overload.



Remedy:

Check encoder power supply wiring and encoder current requirement (Max 200 mA @ 15 V, or 300 mA @ 8 V and 5 V).
EnC2 / 190

Drive encoder trip: Wire break
Cause:

Wire break detected on terminals 1 & 2, 3 & 4, 5 & 6.



Remedy:


  • Check cable continuity.

  • Check encoder cable is plugged into the encoder input port.

  • Check wiring of feedback signals is correct.

  • Check encoder power is set correctly.

  • Replace feedback device.

  • If wire break detection is not required, set Pr 3.40 = 0 to disable.
EnC3 / 191

Drive encoder trip: Phase offset incorrect
Cause:

Phase offset incorrect while running.



Remedy:


  • Check the encoder signal for noise.

  • Check encoder shielding.

  • Check the integrity of the encoder mechanical mounting.

  • Repeat the offset measurement test.
EnC4 / 192

Drive encoder trip: Comms failure
Cause:

Feedback device comms failure.



Remedy:


  • Ensure encoder power supply is correct.

  • Ensure baud rate is correct.

  • Check encoder wiring.

  • Replace feedback device.
EnC5 / 193

Drive encoder trip: Checksum or CRC error
Cause:

Checksum or CRC error detected.



Remedy:


  • Check the encoder signal for noise.

  • Check the encoder cable shielding.

  • With EnDat encoders, check comms resolution and/or carry out auto-configuration Pr 3.41.

  • SSI not ready at start of position transfer.
EnC6 / 194

Drive encoder trip: Encoder error indication
Cause:

Encoder has indicated an error.



Remedy:


  • Replace feedback device.

  • With SSI encoders, check the wiring and encoder supply setting.
EnC7 / 195

Drive encoder trip: Initialization failed
Cause:

Initialization failed.



Remedy:


  • Re-set the drive.

  • Check the correct encoder type is entered into Pr 3.38.

  • Check encoder wiring and power supply.

  • Carry out the auto-configuration Pr 3.41.

  • Replace feedback device.
EnC8 / 196

Drive encoder trip: Auto configuration failed
Cause:

Auto configuration on power up requested and failed.



Remedy:


  • Change Pr 3.41 to 0 and manually enter drive encoder turns (Pr 3.33) and lines per revolution (Pr 3.34).

  • Check the comms resolution.
EnC9 / 197

Drive encoder trip: Position feedback selection error
Cause:

Selected position feedback is from a Solutions Module slot which does not have a module installed.



Remedy:

Check setting of Pr 3.26 (or Pr 21.21).
EnC10 / 198

Drive encoder trip: Phasing failure
Cause:

Encoder phase angle (Pr 3.25 or Pr 21.20) is incorrect.



Remedy:


  • Check the encoder wiring.

  • Perform an autotune to measure the encoder phase angle.

  • Manually enter the correct phase angle.

  • Note: Spurious Enc10 trips in dynamic applications can be disabled by setting Pr 3.08 > 0.
EnC11 / 161

Drive encoder trip: Alignment failure (SINCOS)
Cause:

Alignment failure of analog signals (SINCOS) with digital count. Usually due to noise.



Remedy:


  • Check encoder cable shield.

  • Examine sine and cosine signals for noise.
EnC12 / 162

Drive encoder trip: Hiperface ID failure
Cause:

Hiperface encoder type could not be identified during auto-configuration.



Remedy:


  • Check encoder type can be auto-configured.

  • Check encoder wiring.

  • Enter parameters manually.
EnC13 / 163

Drive encoder trip: EnDat turns error
Cause:

Number of encoder turns read during auto-configuration is not a power of 2.



Remedy:

Select a different type of encoder.
EnC14 / 164

Drive encoder trip: EnDat comms bits error
Cause:

Number of comms bits defining the encoder position within a turn is too large.



Remedy:


  • Select a different type of encoder.

  • Faulty encoder.
EnC15 / 165

Drive encoder trip: PPR calculation error
Cause:

Periods per revolution calculated is < 2 or > 50,000.



Remedy:


  • Linear motor pole pitch / encoder ppr set up is incorrect or out of parameter range.

  • Faulty encoder.
EnC16 / 166

Drive encoder trip: EnDat comms bits limit
Cause:

Number of comms bits per period for a linear encoder exceeds 255.



Remedy:


  • Select a different type of encoder.

  • Faulty encoder.
EnC17 / 167

Drive encoder trip: SINCOS PPR error
Cause:

Periods per revolution for rotary SINCOS encoder is not a power of two.



Remedy:


  • Select a different type of encoder.

  • Faulty encoder.
ENP.Er / 176

Electronic nameplate data error
Cause:

Data error from electronic nameplate stored in selected position feedback device.



Remedy:

Replace feedback device.
Et / 6

External trip from input on terminal 31
Cause:

Triggered by external input.



Remedy:


  • Check terminal 31 signal.

  • Check value of Pr 10.32.

  • Enter 12001 in Pr xx.00 and check for parameter controlling Pr 10.32.

  • Ensure Pr 10.32 or Pr 10.38 (=6) are not being controlled by serial comms.
HF01 – HF24

Data processing / Hardware errors
Cause:

Internal Hardware or Software processing error (CPU, DMAC, Illegal instruction, Watchdog, Heap overflow, etc).



Remedy:

Hardware fault – return drive to supplier.
HF25

Current feedback offset error
Cause: Hardware fault.


Remedy:

  • Return drive to supplier.
HF26

Soft start relay failed to close, soft start monitor failed or braking IGBT short circuit at power up
Cause: Hardware fault.


Remedy:

  • Return drive to supplier.
HF27

Power stage thermistor 1 fault
Cause: Hardware fault.


Remedy:

  • Return drive to supplier.
HF29

Control board thermistor fault
Cause: Hardware fault.


Remedy:

  • Return drive to supplier.
HF30

DCCT wire break trip from power module
Cause: Hardware fault.


Remedy:

  • Return drive to supplier.
It.AC (Trip 20)

Output current overload timed out (I²t)
Cause: Accumulator value reached limit (Pr 4.19). Load jammed, sticking, or incorrect motor parameters.


Remedy:

  • Ensure the load is not jammed / sticking.

  • Ensure that the motor rated current is not set to zero.

  • Check the load on the motor has not changed.

  • If seen during an autotune in servo mode, ensure that the motor rated current Pr 0.46 (Pr 5.07) or Pr 21.07 is current rating of the drive.

  • Tune the rated speed parameter.

  • Check feedback device signal for noise.

  • Check the feedback device mechanical coupling.
It.br (Trip 19)

Braking resistor overload timed out (I²t)
Cause: Braking resistor overload. Accumulator value can be seen in Pr 10.39.


Remedy:

  • Ensure the values entered in Pr 10.30 and Pr 10.31 are correct.

  • Increase the power rating of the braking resistor and change Pr 10.30 and Pr 10.31.

  • If an external thermal protection device is being used and the braking resistor software overload is not required, set Pr 10.30 or Pr 10.31 to 0 to disable the trip.
O.CtL (Trip 23)

Drive control board over temperature
Cause: Control board temperature exceeded limits.


Remedy:

  • Check enclosure / drive fans are still functioning correctly.

  • Check enclosure ventilation paths.

  • Check enclosure door filters.

  • Check ambient temperature.

  • Reduce drive switching frequency.
O.ht1 (Trip 21)

Power device over temperature based on thermal model
Cause: Power device thermal model limit reached.


Remedy:

  • Reduce drive switching frequency.

  • Reduce duty cycle.

  • Decrease acceleration / deceleration rates.

  • Reduce motor load.
O.ht2 (Trip 22)

Heatsink over temperature
Cause: Heatsink temperature too high.


Remedy:

  • Check enclosure / drive fans are still functioning correctly.

  • Check enclosure ventilation paths.

  • Check enclosure door filters.

  • Increase ventilation.

  • Decrease acceleration / deceleration rates.

  • Reduce drive switching frequency.

  • Reduce duty cycle.

  • Reduce motor load.
O.ht3 (Trip 27)

Drive over-temperature based on thermal model
Cause: Thermal model limit reached. The drive will attempt to stop the motor before tripping.


Remedy:

  • Check DC bus ripple.

  • Decrease acceleration / deceleration rates.

  • Reduce duty cycle.

  • Reduce motor load.
OI.AC (Trip 3)

Instantaneous output over current detected
Cause: Over current threshold is Kc/0.45. Short circuit, insulation failure, or incorrect loop gains.


Remedy:

  • Check acceleration / deceleration rate (may be too short).

  • If seen during autotune reduce voltage boost Pr 5.15.

  • Check for short circuit on output cabling.

  • Check integrity of motor insulation.

  • Check feedback device wiring and mechanical coupling.

  • Check feedback signals are free from noise.

  • Is motor cable length within limits?

  • Reduce the values in speed loop gain parameters – Pr 3.10, Pr 3.11 and Pr 3.12.

  • Ensure offset measurement test has been completed.

  • Reduce the values in current loop gain parameters – Pr 4.13 and Pr 4.14.
OI.br (Trip 4)

Braking transistor over-current detected
Cause: Short circuit protection for the braking transistor activated.


Remedy:

  • Check braking resistor wiring.

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

  • Check braking resistor insulation.
O.Ld1 (Trip 26)

Digital output overload
Cause: Total current drawn from 24 V supply and digital outputs exceeds 200 mA.


Remedy:

  • Check total load on digital outputs (terminals 24, 25, 26) and +24 V rail (terminal 22).
O.SPd (Trip 7)

Motor speed has exceeded the over speed threshold
Cause: Speed exceeded threshold in Pr 3.08.


Remedy:

  • Increase the over speed trip threshold in Pr 3.08.

  • Reduce the speed loop P gain (Pr 3.10) to reduce the speed overshoot.
OV (Trip 2)

DC bus voltage has exceeded the peak level or maximum continuous level
Cause: Deceleration too fast, supply disturbances, or motor insulation failure.


Remedy:

  • Increase deceleration ramp (Pr 0.04).

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

  • Check nominal AC supply level.

  • Check for supply disturbances which could cause the DC bus to rise.

  • Check motor insulation.

  • Note: If operating in low voltage DC mode, the overvoltage trip level is 1.45 x Pr 6.46.
PAd (Trip 34)

Keypad has been removed when receiving speed reference from keypad
Cause: Keypad removed during operation.


Remedy:

  • Install the keypad and reset.

  • Change speed reference selector to select speed reference from another source.
PH (Trip 32)

AC voltage input phase loss or large supply imbalance detected
Cause: Phase loss or imbalance. Load level must be between 50 and 100% for trip to occur.


Remedy:

  • Ensure all three phases are present and balanced.

  • Check input voltage levels are correct (at full load).
PS (Trip 5)

Internal power supply fault
Cause: Hardware fault or module issue.


Remedy:

  • Remove any Solutions Modules and reset.

  • Hardware fault – return drive to supplier.
PS.10V (Trip 8)

10 V user power supply current greater than 10 mA
Cause: Overload on 10V rail.


Remedy:

  • Check wiring to terminal 4.

  • Reduce load on terminal 4.
PS.24V (Trip 9)

24V internal power supply overload
Cause: Total user load of drive and Solutions Modules exceeded internal 24V limit.


Remedy:

  • Reduce load and reset.

  • Provide an external 24 V >50 W power supply.

  • Remove any Solutions Modules and reset.
PSAVE.Er (Trip 37)

Power down save parameters in the EEPROM are corrupt
Cause: Power removed while saving parameters.


Remedy:

  • Perform a user save (Pr xx.00 to 1000 or 1001 and reset the drive) to ensure this trip does not occur next time.

  • Power down the drive normally.
rS (Trip 33)

Failure to measure resistance during autotune
Cause: Measurement failure.


Remedy:

  • Check motor power connection continuity.
SAVE.Er (Trip 36)

User save parameters in the EEPROM are corrupt
Cause: Power removed when user parameters were being saved.


Remedy:

  • Perform a user save (Pr xx.00 to 1000 or 1001 and reset the drive) to ensure this trip does not occur next time.
SCL (Trip 30)

Drive RS485 serial comms loss to remote keypad
Cause: Connection loss.


Remedy:

  • Re-instal the cable between the drive and keypad.

  • Check cable for damage.

  • Replace cable.

  • Replace keypad.
SLX.dF (Trip 204, 209)

Solutions Module slot X trip: Type installed in slot X changed
Cause: Module configuration changed.


Remedy:

  • Save parameters and reset.
SLX.Er (Error 1)

Encoder power supply overload
Cause: Current requirement > 200mA (15V) or 300mA (8V/5V) or Excitation output short (Resolver).


Remedy:

  • Check encoder power supply wiring and encoder current requirement.

  • Check the excitation output wiring (if Resolver).
SLX.Er (Error 2)

Wire break
Cause: Feedback signal wire break.


Remedy:

  • Check cable continuity.

  • Check wiring of feedback signals is correct.

  • Check supply voltage or excitation output level.

  • Replace feedback device.
SLX.Er (Error 3)

Phase offset incorrect while running
Cause: Noise or mechanical mounting issue.


Remedy:

  • Check the encoder signal for noise.

  • Check encoder shielding.

  • Check the integrity of the encoder mechanical mounting.

  • Repeat the offset measurement test.
SLX.Er (Error 4)

Feedback device communications failure
Cause: Comms failure.


Remedy:

  • Ensure encoder power supply is correct.

  • Ensure baud rate is correct.

  • Check encoder wiring.

  • Replace feedback device.
SLX.Er (Error 5)

Checksum or CRC error
Cause: Data corruption.


Remedy:

  • Check the encoder signal for noise.

  • Check the encoder cable shielding.
SLX.Er (Error 6)

Encoder has indicated an error
Cause: Internal encoder error.


Remedy:

  • Replace encoder.
SLX.Er (Error 7)

Initialisation failed
Cause: Setup failure.


Remedy:

  • Check the correct encoder type is entered into Pr 15/16/17.15.

  • Check encoder wiring.

  • Check supply voltage level.

  • Replace feedback device.
SLX.Er (Error 8)

Auto configuration on power up has been requested and failed
Cause: Configuration failed.


Remedy:

  • Change the setting of Pr 15/16/17.18 and manually enter the number of turns and lines per revolution.
SLX.Er (Error 9)

Motor thermistor trip
Cause: Motor overheated or continuity issue.


Remedy:

  • Check motor temperature.

  • Check thermistor continuity.
SLX.Er (Error 10)

Motor thermistor short circuit
Cause: Short circuit.


Remedy:

  • Check motor thermistor wiring.

  • Replace motor / motor thermistor.
SLX.Er (Error 11)

Failure of the sincos analog position alignment / Poles not compatible
Cause: Alignment or compatibility issue.


Remedy:

  • Check encoder cable shield.

  • Examine sine and cosine signals for noise.

  • Check that the correct number of resolver poles has been set in Pr 15/16/17.15.
SLX.Er (Error 12)

Encoder type could not be identified during auto-configuration
Cause: Identification failure.


Remedy:

  • Check encoder type can be auto-configured.

  • Check encoder wiring.

  • Enter parameters manually.
SLX.Er (Error 13)

Number of encoder turns read from the encoder during auto-configuration is not a power of 2
Cause: Incorrect turns data.


Remedy:

  • Select a different type of encoder.
SLX.Er (Error 14)

Number of comms bits defining the encoder position is too large
Cause: Configuration issue.


Remedy:

  • Select a different type of encoder.

  • Faulty encoder.
SLX.Er (Error 15)

Calculated periods per revolution either <2 or >50,000
Cause: Auto-configuration data out of range.


Remedy:

  • Linear motor pole pitch / encoder ppr set up is incorrect or out of parameter range.

  • Faulty encoder.
SLX.Er (Error 16)

The number of comms bits per period for a linear encoder exceeds 255
Cause: Configuration issue.


Remedy:

  • Select a different type of encoder.

  • Faulty encoder.
SLX.Er (Error 74)

Solutions Module has overheated
Cause: Over temperature.


Remedy:

  • Check ambient temperature.

  • Check enclosure ventilation.
SLX.Er (Error 39)

User program stack overflow
Cause: Application module software error.


Remedy:

  • Check application program.

  • Refer to SM-Applications Modules manual.
SLX.Er (Error 40)

Unknown error
Cause: Internal error.


Remedy:

  • Please contact supplier.
SLX.Er (Error 41-44)

Parameter Access Error
Cause: 41: Does not exist, 42: Write to read-only, 43: Read from write-only, 44: Value out of range.


Remedy:

  • Check application code parameter access.
SLX.Er (Error 47)

Synchronisation lost with CTSync Master
Cause: Sync loss.


Remedy:

  • Check CTSync connections and configuration.
SLX.Er (Error 48)

RS485 not in user mode
Cause: Port configuration issue.


Remedy:

  • Check RS485 settings.
SLX.Er (Error 50)

Maths error – divide by zero or overflow
Cause: Program math error.


Remedy:

  • Check application program logic.
SLX.Er (Error 51)

Array index out of range
Cause: Program indexing error.


Remedy:

  • Check application program logic.
SLX.Er (Error 53)

DPL program incompatible with target
Cause: Compiled for different hardware.


Remedy:

  • Recompile for correct target.
SLX.Er (Error 54)

DPL task overrun
Cause: Task taking too long to execute.


Remedy:

  • Optimize application program code.
SLX.Er (Error 59)

Drive rejected application module as Sync master
Cause: Sync configuration rejected.


Remedy:

  • Check drive and module settings.
SLX.Er (Error 60)

CTNet hardware failure
Cause: Hardware failure.


Remedy:

  • Please contact your supplier.
SLX.Er (Error 61-63)

CTNet Configuration Error
Cause: 61: Invalid config, 62: Invalid baud-rate, 63: Invalid node ID.


Remedy:

  • Check CTNet configuration.
SLX.Er (Error 64)

Digital Output overload
Cause: Overload on module outputs.


Remedy:

  • Check wiring and load on digital outputs.
SLX.Er (Error 75)

Hardware unavailable
Cause: Module hardware issue.


Remedy:

  • Contact supplier.
SLX.Er (Error 76)

Module type cannot be resolved / not recognized
Cause: Compatibility or identification issue.


Remedy:

  • Check module compatibility.
SLX.Er (Error 77-80)

Inter-Solutions Module comms error
Cause: Communication error between slots (1, 2, 3, or unknown).


Remedy:

  • Check module seating and interactions.
SLX.Er (Error 82)

Communications to drive faulty
Cause: Module-to-Drive comms failure.


Remedy:

  • Reseat module or replace.
SLX.Er
Solutions Module slot X trip
Cause: Solutions Module in slot X or Digitax ST EZMotion has detected a fault.



Remedy:

  • Check value in Pr 15.50, 16.50, or 17.50 depending on the module.

  • Consult the Advanced User Guide or Solutions Module User Guide.

  • See sub-categories below for specific error codes:



Common Sub-codes (Automation/EZMotion):

41-44: Parameter access errors

74: Module overheat

104: Following error

121, 125, 128, 130, 143, 154, 157, 174: File corruption (Consult factory)

175: Module output overload
SLX.HF
Solutions Module hardware fault
Cause: Solutions Module in slot X has a hardware fault.



Remedy:

  • Ensure Solutions Module is installed correctly.

  • Return Solutions Module to supplier.
SLX.nF
Solutions Module removed
Cause: Solutions Module in slot X has been removed.



Remedy:

  • Ensure Solutions Module is installed correctly.

  • Re-install Solutions Module.

  • Save parameters and reset drive.
SL.rtd
Solutions Module routing error
Cause: Drive mode has changed and Solutions Module parameter routing is now incorrect.



Remedy:

  • Press reset.

  • If the trip persists, contact the supplier of the drive.
SLX.tO
Solutions Module watchdog timeout
Cause: Solutions Module watchdog timeout.



Remedy:

  • Press reset.

  • If the trip persists, contact the supplier of the drive.
t010
User defined trip
Cause: User trip defined in 2nd processor Solutions Module code (Error 10).



Remedy:

  • SM-Applications program must be interrogated to find the cause of this trip.
t038
User defined trip
Cause: User trip defined in 2nd processor Solutions Module code (Error 38).



Remedy:

  • SM-Applications program must be interrogated to find the cause of this trip.
t040 to t089
User defined trip range
Cause: User trip defined in 2nd processor Solutions Module code (Errors 40 to 89).



Remedy:

  • SM-Applications program must be interrogated to find the cause of this trip.
th
Motor thermistor trip
Cause: Motor temperature high or monitoring fault.



Remedy:

  • Check motor temperature.

  • Check thermistor continuity.

  • Set Pr 7.15 = VOLt and reset the drive to disable this function if not required.
thS
Motor thermistor short circuit
Cause: Motor thermistor wiring short circuit.



Remedy:

  • Check motor thermistor wiring.

  • Replace motor / motor thermistor.

  • Set Pr 7.15 = VOLt and reset the drive to disable this function.
tunE*
Autotune stopped
Cause: Autotune stopped before completion. (Error 18)



Remedy:

  • The drive has tripped out during the autotune.

  • The red stop key has been pressed during the autotune.

  • The Safe Torque Off signal (terminal 31) was active during the autotune procedure.
tunE1*
Position feedback error during inertia test
Cause: The position feedback did not change or required speed could not be reached during the inertia test. (Error 11)



Remedy:

  • Ensure the motor is free to turn (i.e., brake was released).

  • Check feedback device wiring is correct.

  • Check feedback parameters are set correctly.

  • Check encoder coupling to motor.
tunE2*
Position feedback direction incorrect
Cause: Position feedback direction incorrect or motor could not be stopped during the inertia test. (Error 12)



Remedy:

  • Check motor cable wiring is correct.

  • Check feedback device wiring is correct.

  • Swap any two motor phases.
tunE3*
Commutation signal error
Cause: Drive encoder commutation signals connected incorrectly or measured inertia out of range. (Error 13)



Remedy:

  • Check motor cable wiring is correct.

  • Check feedback device U, V and W commutation signal wiring is correct.
tunE4*
U commutation signal fail
Cause: Drive encoder U commutation signal fail during an autotune. (Error 14)



Remedy:

  • Check feedback device U phase commutation wires continuity.

  • Replace encoder.
tunE5*
V commutation signal fail
Cause: Drive encoder V commutation signal fail during an autotune. (Error 15)



Remedy:

  • Check feedback device V phase commutation wires continuity.

  • Replace encoder.
tunE6*
W commutation signal fail
Cause: Drive encoder W commutation signal fail during an autotune. (Error 16)



Remedy:

  • Check feedback device W phase commutation wires continuity.

  • Replace encoder.
tunE7*
Motor poles set incorrectly
Cause: Motor number of poles set incorrectly. (Error 17)



Remedy:

  • Check lines per revolution for feedback device.

  • Check the number of poles in Pr 5.11 is set correctly.
UP ACC
Onboard PLC access error
Cause: Onboard PLC program: cannot access Onboard PLC program file on drive. (Error 98)



Remedy:

  • Disable drive – write access is not allowed when the drive is enabled.

  • Another source is already accessing Onboard PLC program – retry once other action is complete.
UP div0
PLC divide by zero
Cause: Onboard PLC program attempted divide by zero. (Error 90)



Remedy:

  • Check program.
UP OFL
PLC stack overflow
Cause: Onboard PLC program variables and function block calls using more than the allowed RAM space. (Error 95)



Remedy:

  • Check program.
UP ovr
PLC parameter write range
Cause: Onboard PLC program attempted out of range parameter write. (Error 94)



Remedy:

  • Check program.
UP PAr
PLC non-existent parameter
Cause: Onboard PLC program attempted access to a non-existent parameter. (Error 91)



Remedy:

  • Check program.
UP ro
PLC read-only write
Cause: Onboard PLC program attempted write to a read-only parameter. (Error 92)



Remedy:

  • Check program.
UP So
PLC write-only read
Cause: Onboard PLC program attempted read of a write-only parameter. (Error 93)



Remedy:

  • Check program.
UP udF
PLC un-defined trip
Cause: Onboard PLC program un-defined trip. (Error 97)



Remedy:

  • Check program.
UP uSEr
PLC requested trip
Cause: Onboard PLC program requested a trip. (Error 96)



Remedy:

  • Check program.
UV
DC bus under voltage
Cause: DC bus under voltage threshold reached.



Remedy:

  • Check AC supply voltage level.

  • 200V Drive: UV Threshold: 175 Vdc, Reset: 215 Vdc.

  • 400V Drive: UV Threshold: 330 Vdc, Reset: 425 Vdc.
HF01 to HF16
Hardware faults
Cause:

These indicate serious internal problems.


Remedy:

Cannot be reset. The drive is inactive after one of these trips and the display shows HFxx.
HF17 to HF32, SL1.HF, SL2.HF, SL3.HF
Non-resetable trips
Cause:

Internal drive fault.


Remedy:

Cannot be reset.
EEF
EEF trip
Cause:

EEPROM failure or corruption.


Remedy:

Cannot be reset unless a code to load defaults is first entered in Pr x.00 or Pr 11.43.
C.Boot, C.Busy, C.Chg, C.Optn, C.Rdo, C.Err, C.dat, C.FULL, C.Acc, C.rtg, C.Typ, C.cpr, C.Prod
SMARTCARD trips
Cause:

Issues related to SMARTCARD operation (read/write/data).


Remedy:

SMARTCARD trips have priority 5 during power up. Check SMARTCARD status and data.
PS.24V, EnC1
Encoder power supply trips
Cause:

Power supply fault for encoder.


Remedy:

These trips can only override the following priority 5 trips: EnC2 – EnC8 or Enc11 – En17. Check encoder wiring and supply.
OI.AC, OI.br, OIAC.P, OIbr.P, OidC.P
Normal trips with extended reset
Cause:

Overcurrent or overload conditions requiring cooldown.


Remedy:

Can be reset after 10.0s.
Old1, cL2, cL3, SCL
Non-important trips
Cause:

Various minor trip conditions.


Remedy:

If bit 0 of Pr 10.37 is 1 the drive will stop before tripping.
PH
Phase loss
Cause:

One or more input phases are missing.


Remedy:

The drive attempts to stop before tripping. Check input supply.
O.ht3
Drive over-heat based on thermal model
Cause:

Thermal model suggests drive overheating.


Remedy:

The drive attempts to stop before tripping, but if it does not stop within 10s the drive will automatically trip. Check cooling.
UV
Self resetting trips (Under Voltage)
Cause:

Supply voltage is below specification.


Remedy:

Under voltage trip cannot be reset by the user, but is automatically reset by the drive when the supply voltage is with specification.
br.rS
Braking resistor overload
Cause:

Braking resistor I2t accumulator (Pr 10.39) in the drive has reached 75.0 % of the value at which the drive will trip and the braking IGBT is active.


Remedy:

Check braking resistor sizing and duty cycle.
Hot
Heatsink or control board or inverter IGBT over temperature
Cause:


  • The drive heatsink temperature has reached a threshold (potential O.ht2 trip).

  • The ambient temperature around the control PCB is approaching the over temperature threshold (potential O.CtL trip).



Remedy:

Reduce load, check fans, or lower ambient temperature.
OVLd
Motor overload
Cause:

The motor I2t accumulator (Pr 4.19) in the drive has reached 75 % of the value at which the drive will be tripped and the load on the drive is >100 %.


Remedy:

Reduce motor load.
Auto tune
Autotune in progress
Cause:

The autotune procedure has been initialised. ‘Auto’ and ‘tunE’ will flash alternatively on the display.


Remedy:

Wait for autotune to complete.
Lt
Limit switch is active
Cause:

Indicates that a limit switch is active and that it is causing the motor to be stopped (i.e. forward limit switch with forward reference etc.).


Remedy:

Check limit switches and machine position.
PLC
Onboard PLC program is running
Cause:

An Onboard PLC program is installed and running.


Remedy:

Information only. The lower display will flash ‘PLC’ once every 10 s.
ACUU
AC Supply loss
Cause:

The drive has detected that the AC supply has been lost and is attempting to maintain the DC bus voltage by decelerating the motor.


Remedy:

Check mains supply.
dc
DC applied to the motor
Cause:

The drive is applying DC injection braking.


Remedy:

Status indication.
dEC
Decelerating
Cause:

The drive is decelerating the motor.


Remedy:

Status indication.
inh
Inhibit
Cause:

The drive is inhibited and cannot be run. The drive enable signal is not applied to terminal 31 or Pr 6.15 is set to 0.


Remedy:

Apply enable signal to terminal 31 or check Pr 6.15.
POS
Positioning
Cause:

The drive is positioning/orientating the motor shaft.


Remedy:

Status indication.
rdY
Ready
Cause:

The drive is ready to be run.


Remedy:

Status indication.
SCAn
Scanning
Cause:

Regen > The drive is enabled and is synchronising to the line.


Remedy:

Status indication.
StoP
Stop or holding zero speed
Cause:

The drive is holding zero speed. Regen > The drive is enabled but the AC voltage is too low, or the DC bus voltage is still rising or falling.


Remedy:

Status indication.
triP
Trip condition
Cause:

The drive has tripped and is no longer controlling the motor.


Remedy:

Check the trip code on the lower display and resolve the fault.
boot
Booting
Cause:

A parameter set is being transferred from the SMARTCARD to the drive during power-up.


Remedy:

Wait for transfer to complete. Refer to User Guide for details.
cArd
Card Write
Cause:

The drive is writing a parameter set to the SMARTCARD during power-up.


Remedy:

Wait for write to complete.
loAding
Loading
Cause:

The drive is writing information to a Solutions Module.


Remedy:

Status indication.

Safety Note: If the drive displays a code starting with “HF” (e.g., HF08), this indicates a Hardware Fault. These represent internal power stage failures. Do not attempt to reset an HF trip multiple times, as this can cause further internal damage.

How to Read Digitax ST Faults via CTSoft & Connect

In 2026, troubleshooting a Digitax ST is most effective when using CTSoft (the legacy commissioning tool) or Control Techniques Connect software. These tools allow you to look deeper into the drive’s parameters than the 2-digit LED display allows.

  • Trip History (Menu 10): The Digitax ST stores the last 10 trips in Parameters 10.20 through 10.29. Using software, you can view the “Trip Time” (measured in drive run-hours) to correlate the fault with machine events.
  • SM-Option Modules: The Digitax ST features two slots for SM-Option modules (e.g., SM-Encoder, SM-Applications). If a trip occurs in a module, the drive will often display a sub-trip code to identify whether Slot 1 or Slot 2 caused the issue.
  • Real-Time Monitoring: Use the software to trace Parameter 04.02 (Active Torque Reference) and 03.02 (Speed Feedback). Spikes in these values just before a trip can indicate mechanical binding or encoder signal noise.
  • SmartStick: If you use a SmartStick (the green memory stick), you can easily upload the fault log and parameter set to a PC or clone it to a replacement drive for fast recovery.

Frequently Asked Questions (FAQ)

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

A: A Trip (Solid code) is a protective shutdown that stops the motor immediately. A Warning (Flashing code) indicates the drive is nearing a limit—such as O.Ld1 (Load Warning) or Hot (Heatsink temperature)—but it will keep the motor running until the condition becomes critical.

Q: How do I reset a Digitax ST fault?

A: Once the root cause (such as a mechanical jam or cable issue) is resolved, you can reset the drive via:

  • Pressing the Red Reset Button on the keypad.
  • Cycling the Main Power (Wait 30 seconds for the display to go dark before reapplying power).
  • Toggling a Digital Input assigned to the “Reset” function (Terminal 31 is the default enable/reset).

Q: What does “ih” mean on the display?

A: “ih” stands for Inhibit. This is a status code, not a fault. It means the drive is healthy but cannot run because the Secure Torque Off (STO) / Enable signal is missing from Terminal 31. Once 24V is applied, the display should change to “rd” (Ready).

Q: My drive shows “Enc1,” what should I check?

A: Enc1 is a Primary Encoder Fault. Check the motor encoder cable for damage, ensure the connector is securely fastened, and verify that the encoder shield is properly grounded. In high-vibration applications, the encoder itself may have failed.

Q: Where is the trip history stored?

A: The trip history is stored in the non-volatile memory in Menu 10. Parameter 10.20 always contains the most recent trip data, and this log is preserved even when the drive is powered down.