Unidrive SP Drive Fault Codes (2026)

Categories: Drives, PLC & HMI, Faults & Alarm

Unidrive SP Drive Fault Codes (2026) – The Control Techniques Unidrive SP (Solutions Platform) is one of the most successful legacy drives ever manufactured. Even in 2026, thousands of these units remain in service due to their incredible flexibility in handling open-loop, closed-loop, servo, and regenerative applications. 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 It.AC (Motor Overload).

This guide is designed to help maintenance teams decode these strings, manage the three SM-option slots, and utilize legacy software tools to maintain these workhorse drives.

Unidrive SP Fault Codes Reference Table

Below is the reference list of trips for the Unidrive SP. These codes appear on either the standard LED keypad or the advanced LCD multilingual keypad.

Fault Code and MeaningCause and Remedy
OI.AC (3)

Instantaneous output over current detected: peak output current greater than 225%
Cause: Acceleration / deceleration rate is too short or circuit issues.


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.

  • Is motor cable length within limits for that frame size?

  • Reduce the values in speed loop gain parameters – Pr 3.10, Pr 3.11 and Pr 3.12 (and servo modes only).

  • Has offset measurement test been completed? (servo mode only).

  • Reduce the values in current loop gain parameters – Pr 4.13 and Pr 4.14 (closed loop vector and servo modes only).
br.th (10)

Internal braking resistor thermistor temperature monitoring fail (size 0 only)
Cause: Braking resistor issue or configuration error.


Remedy:

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

  • If an internal brake resistor is installed: Ensure that the internal braking resistor thermistor is connected correctly.

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

  • Replace the internal braking resistor.
C.Acc (185)

SMARTCARD trip: SMARTCARD Read / Write fail
Cause: Card installation or write error.


Remedy:

  • Check SMARTCARD is installed / located correctly.

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

  • Replace SMARTCARD.
C.boot (177)

SMARTCARD trip: The menu 0 parameter modification cannot be saved
Cause: Necessary file has not been created on the SMARTCARD.


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: SMARTCARD can not perform the required function
Cause: Card 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 an occupied location.


Remedy:

  • Erase data in data location.

  • Write data to an alternative data location.
C.cPr (188)

SMARTCARD trip: The values stored in the drive and the values in the data block on the SMARTCARD are different
Cause: Value mismatch.


Remedy:

  • Press the red reset button.
C.dAt (183)

SMARTCARD trip: Data location specified does not contain any data
Cause: Empty data block.


Remedy:

  • Ensure data block number is correct.
C.Err (182)

SMARTCARD trip: SMARTCARD data is corrupted
Cause: Corrupted card data or bad connection.


Remedy:

  • Ensure the card is located correctly.

  • Erase data and retry.

  • Replace SMARTCARD.
C.Full (184)

SMARTCARD trip: SMARTCARD full
Cause: No space left on card.


Remedy:

  • Delete a data block or use different SMARTCARD.
cL2 (28)

Analog input 2 current loss (current mode)
Cause: Signal loss on terminal 7.


Remedy:

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

Analog input 3 current loss (current mode)
Cause: Signal loss on terminal 8.


Remedy:

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

Trip initiated from the control word (Pr 6.42)
Cause: Control word initiation.


Remedy:

  • Disable the control word by setting Pr 6.43 to 0 or check setting of Pr 6.42.
ConF.P (111)

The number of power modules installed no longer matches the value stored in Pr 11.35
Cause: Configuration mismatch in power modules.


Remedy:

  • Ensure that all power modules are correctly connected.

  • Ensure that all power modules have powered up correctly.

  • Ensure that the value in Pr 11.35 matches the number of power modules connected.
C.OPtn (180)

SMARTCARD trip: Solutions Modules installed are different between source drive and destination drive
Cause: Module mismatch.


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


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: SMARTCARD has the Read Only bit set
Cause: Write access denied.


Remedy:

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

  • Ensure the drive is not writing to data locations 500 to 999 on the card.
C.rtg (186)

SMARTCARD trip: The voltage and/or current rating of the source and destination drives are different
Cause: Drive rating dependent parameters differ. Parameters with RA coding will not transfer.


Remedy:

  • Press the red reset button.

  • Note: Drive rating parameters will be set to their default values (e.g., Standard ramp voltage, Current limits, Motor rated current/voltage).
C.TyP (187)

SMARTCARD trip: SMARTCARD parameter set not compatible with drive
Cause: Source and destination drive types differ.


Remedy:

  • Press the reset button.

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

Two or more parameters are writing to the same destination parameter
Cause: Parameter duplication.


Remedy:

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

EEPROM data corrupted
Cause: Drive mode becomes open loop and serial comms timeout.


Remedy:

  • This trip can only be cleared by loading default parameters and saving parameters.
EnC1 (189)

Drive encoder trip: Encoder power supply overload
Cause: Excessive current draw.


Remedy:

  • Check encoder power supply wiring and encoder current requirement.

  • Maximum current = 200mA @ 15V, or 300mA @ 8V and 5V.
EnC2 (190)

Drive encoder trip: Wire break (Drive encoder terminals 1 & 2, 3 & 4, 5 & 6)
Cause: Connection issue or faulty device.


Remedy:

  • Check cable continuity.

  • Check wiring of feedback signals is correct.

  • Check encoder power supply is set correctly in Pr 3.36.

  • Replace feedback device.

  • If wire break detection is not required, set Pr 3.40 = 0 to disable the Enc2 trip.
EnC3 (191)

Drive encoder trip: Phase offset incorrect while running
Cause: Noise, shielding, or mounting issues.


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: Feedback device comms failure
Cause: Communication or power 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: Noise or configuration error.


Remedy:

  • Check the encoder signal for noise.

  • Check the encoder cable shielding.

  • With EnDat encoders, check the comms resolution and/or carry out the auto-configuration Pr 3.41.
EnC6 (194)

Drive encoder trip: Encoder has indicated an error
Cause: Internal encoder error.


Remedy:

  • Replace feedback device.

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

Drive encoder trip: Initialisation failed
Cause: Setup or wiring failure.


Remedy:

  • Re-set the drive.

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

  • Check encoder wiring.

  • Check encoder power supply is set correctly.

  • Carry out the auto-configuration Pr 3.41.

  • Replace feedback device.
EnC8 (196)

Drive encoder trip: Auto configuration on power up has been requested and failed
Cause: Configuration failure.


Remedy:

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

  • Check the comms resolution.
EnC9 (197)

Drive encoder trip: Position feedback selected is from a Solutions Module without speed/position installed
Cause: Incorrect module selection.


Remedy:

  • Check setting of Pr 3.26 (or Pr 21.21 if the second motor parameters have been enabled).
EnC10 (198)

Drive encoder trip: Servo mode phasing failure because encoder phase angle is incorrect
Cause: Incorrect phase angle (Pr 3.25 or Pr 21.20) or spurious trips in dynamic apps.


Remedy:

  • Check the encoder wiring.

  • Perform an autotune to measure the encoder phase angle or manually enter the correct phase angle into Pr 3.25 (or Pr 21.20).

  • This trip can be disabled by setting the overspeed threshold in Pr 3.08 to a value greater than zero (use caution).
Enc11 (161)

Drive encoder trip: Failure occurred during alignment of analog signals of a SINCOS encoder
Cause: Usually due to noise on the sine and cosine signals.


Remedy:

  • Check encoder cable shield.

  • Examine sine and cosine signals for noise.
Enc12 (162)

Drive encoder trip: Hiperface encoder – The 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.
Enc13 (163)

Drive encoder trip: EnDat encoder – Number of turns read during auto-configuration is not a power of 2
Cause: Incompatible encoder turns.


Remedy:

  • Select a different type of encoder.
Enc14 (164)

Drive encoder trip: EnDat encoder – Comms bits defining position within a turn is too large
Cause: Comms bits too large.


Remedy:

  • Select a different type of encoder.

  • Faulty encoder.
Enc15 (165)

Drive encoder trip: Number of periods per revolution calculated is either less than 2 or greater than 50,000
Cause: Linear motor pole pitch / encoder ppr set up is incorrect or out of parameter range.


Remedy:

  • Check Pr 5.36 = 0 or Pr 21.31 = 0.

  • Faulty encoder.
Enc16 (166)

Drive encoder trip: EnDat encoder – The number of comms bits per period for a linear encoder exceeds 255
Cause: Exceeds limit.


Remedy:

  • Select a different type of encoder.

  • Faulty encoder.
Enc17 (167)

Drive encoder trip: The periods per revolution obtained during auto-configuration for a rotary SINCOS encoder is not a power of two
Cause: Incompatible periods per revolution.


Remedy:

  • Select a different type of encoder.

  • Faulty encoder.
ENP.Er (176)

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


Remedy:

  • Replace feedback device.
Et (6)

External trip
Cause: External signal via terminal 31.


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

Data processing error: CPU address error
Cause: Hardware fault.


Remedy:

  • Return drive to supplier.
HF02
Data processing error: DMAC address error
Cause:
Hardware fault.


Remedy:
Return drive to supplier.
HF03
Data processing error: Illegal instruction
Cause:
Hardware fault.


Remedy:
Return drive to supplier.
HF04
Data processing error: Illegal slot instruction
Cause:
Hardware fault.


Remedy:
Return drive to supplier.
HF05
Data processing error: Undefined exception
Cause:
Hardware fault.


Remedy:
Return drive to supplier.
HF06
Data processing error: Reserved exception
Cause:
Hardware fault.


Remedy:
Return drive to supplier.
HF07
Data processing error: Watchdog failure
Cause:
Hardware fault.


Remedy:
Return drive to supplier.
HF08
Data processing error: Level 4 crash
Cause:
Hardware fault.


Remedy:
Return drive to supplier.
HF09
Data processing error: Heap overflow
Cause:
Hardware fault.


Remedy:
Return drive to supplier.
HF10
Data processing error: Router error
Cause:
Hardware fault.


Remedy:
Return drive to supplier.
HF11
Data processing error: Access to EEPROM failed
Cause:
Hardware fault.


Remedy:
Return drive to supplier.
HF12
Data processing error: Main program stack overflow
Cause:
Hardware fault.


Remedy:
Return drive to supplier.
HF13
Data processing error: Software incompatible with hardware
Cause:
Hardware or software fault.


Remedy:
Return drive to supplier.
HF17 (217)
Multi-module system thermistor short circuit or open circuit
Cause:
Hardware fault.


Remedy:
Return drive to supplier.
HF18 (218)
Multi-module system interconnect cable error
Cause:
Hardware fault.


Remedy:
Return drive to supplier.
HF19 (219)
Temperature feedback multiplexing failure
Cause:
Hardware fault.


Remedy:
Return drive to supplier.
HF20 (220)
Power stage recognition: serial code error
Cause:
Hardware fault.


Remedy:
Return drive to supplier.
HF21 (221)
Power stage recognition: unrecognised frame size
Cause:
Hardware fault.


Remedy:
Return drive to supplier.
HF22 (222)
Power stage recognition: multi module frame size mismatch
Cause:
Hardware fault.


Remedy:
Return drive to supplier.
HF23 (223)
Power stage recognition: multi module voltage or current rating mismatch
Cause:
Hardware fault.


Remedy:
Return drive to supplier.
HF24 (224)
Power stage recognition: unrecognised drive size
Cause:
Hardware fault.


Remedy:
Return drive to supplier.
HF25 (225)
Current feedback offset error
Cause:
Hardware fault.


Remedy:
Return drive to supplier.
HF26 (226)
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 (227)
Power stage thermistor 1 fault
Cause:
Hardware fault.


Remedy:
Return drive to supplier.
HF28 (228)
Power stage thermistor 2 fault, or internal fan fault (size 3)
Cause:
Hardware fault.


Remedy:
Return drive to supplier.
HF29 (229)
Control board thermistor fault
Cause:
Hardware fault.


Remedy:
Return drive to supplier.
HF30 (230)
DCCT wire break trip from power module
Cause:
Hardware fault.


Remedy:
Return drive to supplier.
HF31 (231)
Internal capacitor bank fan failure (size 4 and larger) or a module has not powered up
Cause:
AC or DC power supply issue or Hardware fault.


Remedy:

  • Check the AC or DC power supply to all modules in a multi-module parallel drive.

  • If the AC or DC power supply is present, or if this is a single drive, then there is a hardware fault – return drive to the supplier.
HF32 (232)
Power stage – Identification and trip information serial code error
Cause:
Hardware fault.


Remedy:
Return drive to the supplier.
It.AC (20)
Output current overload timed out (I²t)
Cause:
Accumulator value can be seen in Pr 4.19.


Remedy:

  • Ensure the load is not jammed / sticking.

  • 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 ≤ Heavy Duty current rating of the drive.

  • Tune the rated speed parameter (closed loop vector only).

  • Check feedback device signal for noise.

  • Check the feedback device mechanical coupling.
It.br (19)
Braking resistor overload timed out (I²t)
Cause:
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.
L.SYnC (39)
Drive failed to synchronize to the supply voltage in Regen mode
Cause:
Synchronization failure.


Remedy:
Refer to the Diagnostics chapter in the Unidrive SP Regen Installation Guide.
O.CtL (23)
Drive control board over temperature
Cause:
Control board overheating.


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 (21)
Power device over temperature based on thermal model
Cause:
Power device overheating.


Remedy:

  • Reduce drive switching frequency.

  • Reduce duty cycle.

  • Decrease acceleration / deceleration rates.

  • Reduce motor load.
O.ht2 (22)
Heatsink over temperature
Cause:
Heatsink overheating.


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.
Oht2.P (105)
Power module heatsink over temperature
Cause:
Power module heatsink overheating.


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 (27)
Drive over-temperature based on thermal model
Cause:
Thermal model trip. The drive will attempt to stop the motor before tripping.


Remedy:

  • Check enclosure / drive fans are still functioning correctly.

  • Check enclosure ventilation paths.

  • Check enclosure door filters.

  • Increase ventilation.

  • Decrease acceleration / deceleration rates.

  • Reduce duty cycle.

  • Reduce motor load.
Oht4.P (102)
Power module rectifier over temperature or input snubber resistor over temperature (size 4 and above)
Cause:
Rectifier or snubber overheating.


Remedy:

  • Check for supply imbalance.

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

  • 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.
OI.AC (3)
Instantaneous output over current detected: peak output current greater than 225%
Cause:
Short circuit or incorrect tuning parameters.


Remedy:

  • Acceleration / deceleration rate is 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.

  • Check feedback device mechanical coupling.

  • Check feedback signals are free from noise.

  • Is motor cable length within limits for that frame size?

  • Reduce the values in speed loop gain parameters – Pr 3.10, Pr 3.11 and Pr 3.12 (and servo modes only).

  • Has offset measurement test been completed? (servo mode only).

  • Reduce the values in current loop gain parameters – Pr 4.13 and Pr 4.14 (closed loop vector and servo modes only).
OIAC.P (104)
Power module over current detected from the module output currents
Cause:
Module output overcurrent.


Remedy:

  • Acceleration / deceleration rate is 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.

  • Check feedback device mechanical coupling.

  • Check feedback signals are free from noise.

  • Is motor cable length within limits for that frame size?

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

  • Has offset measurement test been completed? (servo mode only).

  • Reduce values in current loop gain parameters – Pr 4.13 and Pr 4.14.
OI.br (4)
Braking transistor over-current detected: short circuit protection activated
Cause:
Braking transistor short circuit.


Remedy:

  • Check braking resistor wiring.

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

  • Check braking resistor insulation.
OIbr.P (103)
Power module braking IGBT over current
Cause:
Braking IGBT over current.


Remedy:

  • Check braking resistor wiring.

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

  • Check braking resistor insulation.
OIdC.P (109)
Power module over current detected from IGBT on state voltage monitoring
Cause:
Vce IGBT protection activated.


Remedy:
Check motor and cable insulation.
O.Ld1 (26)
Digital output overload
Cause:
Total current drawn from 24V supply and digital outputs exceeds 200mA.


Remedy:
Check total load on digital outputs (terminals 24,25,26) and +24V rail (terminal 22).
O.SPd (7)
Motor speed has exceeded the over speed threshold
Cause:
Speed exceeded 1.2 x Pr 1.06 or Pr 1.07.


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 (2)
DC bus voltage has exceeded the peak level or the maximum continuous level for 15 seconds
Cause:
DC bus overvoltage.


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 (notches).

  • Check motor insulation.

  • If operating in low voltage DC mode, the overvoltage trip level is 1.45 x Pr 6.46.
OV.P (106)
Power module DC bus voltage has exceeded the peak level or the maximum continuous level for 15 seconds
Cause:
DC bus overvoltage (Power module).


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 (notches).

  • Check motor insulation.

  • If operating in low voltage DC mode, the overvoltage trip level is 1.45 x Pr 6.46.
PAd (34)
Keypad has been removed when the drive is receiving the speed reference from the keypad
Cause:
Keypad removal.


Remedy:

  • Install keypad and reset.

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


Remedy:

  • Ensure all three phases are present and balanced.

  • Check input voltage levels are correct (at full load).
PH.P (107)
Power module phase loss detection
Cause:
Phase loss or imbalance.


Remedy:

  • Ensure all three phases are present and balanced.

  • Check input voltage levels are correct (at full load).
PS (5)
Internal power supply fault
Cause:
Hardware fault.


Remedy:

  • Remove any Solutions Modules and reset.

  • Hardware fault – return drive to supplier.
PS.10V (8)
10V user power supply current greater than 10mA
Cause:
Overload on 10V supply.


Remedy:

  • Check wiring to terminal 4.

  • Reduce load on terminal 4.
PS.24V (9)
24V internal power supply overload
Cause:
Total user load exceeds internal 24V limit.


Remedy:

  • Reduce load and reset.

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

  • Remove any Solutions Modules and reset.
PS.P (108)
Power module power supply fail
Cause:
Power supply failure.


Remedy:

  • Remove any Solutions Modules and reset.

  • Hardware fault – return drive to supplier.
PSAVE.Er (37)
Power down save parameters in the EEPROM are corrupt
Cause:

Indicates that the power was removed when power down save parameters were being saved. The drive will revert back to the power down parameter set that was last saved successfully.



Remedy:


  • Perform a user save (Pr xx.00 to 1000 or 1001 and reset the drive).

  • Power down the drive normally to ensure this trip does not occur the next time the drive is powered up.
rS (33)
Failure to measure resistance
Cause:

Failure to measure resistance during autotune or when starting in open loop vector mode 0 or 3.



Remedy:


  • Check motor power connection continuity.
SAVE.Er (36)
User save parameters in the EEPROM are corrupt
Cause:

Indicates that the power was removed when user parameters were being saved. The drive will revert back to the user parameter set that was last saved successfully.



Remedy:


  • Perform a user save (Pr xx.00 to 1000 or 1001 and reset the drive).
SCL (30)
Drive RS485 serial comms loss to remote keypad
Cause:

Communication loss between the drive and the remote keypad.



Remedy:


  • Reinstall the cable between the drive and keypad.

  • Check cable for damage.

  • Replace cable.

  • Replace keypad.
SLX.dF (204, 209, 214)
Solutions Module slot X trip
Cause:

Solutions Module type installed in slot X changed.



Remedy:


  • Save parameters and reset.
SLX.Er – Code 1
Feedback Module: Power supply overload
Cause:

Encoder power supply overload or Excitation output short circuit (SM-Resolver).



Remedy:


  • Check encoder power supply wiring.

  • Check encoder current requirement (Max 200mA @ 15V, or 300mA @ 8V/5V).

  • Check the excitation output wiring.
SLX.Er – Code 2
Feedback Module: Wire break
Cause:

Wire break detected.



Remedy:


  • Check cable continuity.

  • Check wiring of feedback signals.

  • Check supply voltage or excitation output level.

  • Replace feedback device.
SLX.Er – Code 3
Feedback Module: Phase offset incorrect
Cause:

Phase offset incorrect while running.



Remedy:


  • Check the encoder signal for noise.

  • Check encoder shielding.

  • Check integrity of encoder mechanical mounting.

  • Repeat offset measurement test.
SLX.Er – Code 4
Feedback Module: Comms failure
Cause:

Feedback device communications failure.



Remedy:


  • Ensure encoder power supply is correct.

  • Ensure baud rate is correct.

  • Check encoder wiring.

  • Replace feedback device.
SLX.Er – Code 6
Feedback Module: Encoder Error
Cause:

Encoder has indicated an internal error.



Remedy:


  • Replace encoder.
SLX.Er – Code 7
Feedback Module: Initialization failed
Cause:

Initialization failed.



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 – Code 9
Feedback Module: Motor thermistor trip
Cause:

Motor thermistor trip detected.



Remedy:


  • Check motor temperature.

  • Check thermistor continuity.
SLX.Er – Code 74
Solutions Module Overheated
Cause:

Solutions Module has overheated.



Remedy:


  • Check ambient temperature.

  • Check enclosure ventilation.
SLX.Er – Code 39
Automation Module: Stack overflow
Cause:

User program stack overflow.



Remedy:


  • Check user program logic.

  • See Diagnostics section in relevant Solutions Module User Guide.
SLX.Er – Code 40
Automation Module: Unknown error
Cause:

Unknown error.



Remedy:


  • Please contact supplier.
SLX.Er – Code 44
Automation Module: Parameter range
Cause:

Parameter value out of range.



Remedy:


  • Check program code writing to parameters.
SLX.Er – Code 50
Automation Module: Maths error
Cause:

Maths error – divide by zero or overflow.



Remedy:


  • Check calculation logic in user program.
SLX.Er – Code 64
Automation Module: Digital Output
Cause:

Digital Output overload.



Remedy:


  • Check load on digital outputs.
SLX.Er – Code 82
Automation Module: Comms Fault
Cause:

Communications to drive faulty.



Remedy:


  • Check module seating and connections.
SLX.Er – Code 2 (I/O)
I/O Module: Input/Output Error
Cause:

Analog input current too high/low or Digital input overload (depends on module type).



Remedy:


  • Check wiring and signal levels.
SLX.Er – Code 65 (Fieldbus)
Fieldbus Module: Network loss
Cause:

Network loss detected on SM-PROFIBUS, DeviceNet, CANOpen, etc.



Remedy:


  • Check network cabling.

  • Check master controller status.
SLX.Er – Code 75 (Fieldbus)
Fieldbus Module: Drive not responding
Cause:

The drive is not responding (SM-Ethernet, SM-EtherCAT).



Remedy:


  • Check communication path to drive.

  • Reset module.
SLX.Er

Solutions Module slot X trip: Solutions Module in slot X has detected a fault
Cause:

The Solutions Module has detected an internal error. Common error codes (Pr 15/16/17.50):

  • 1: Power supply overloaded

  • 2: SLM version is too low

  • 3: DriveLink error

  • 4: Incorrect switching frequency selected

  • 5: Feedback source selection incorrect

  • 6: Encoder error

  • 74: Solutions module over temperature




Remedy:


  • Check value in Pr 15/16/17.50.

  • See the Diagnostics section in the SM-SLM User Guide for more information.
SLX.HF

Solutions Module slot X trip: Solutions Module X hardware fault
Cause:

Hardware fault detected in the module.



Remedy:


  • Ensure Solutions Module is installed correctly.

  • Return Solutions Module to supplier.
SLX.nF

Solutions Module slot X trip: Solutions Module has been removed
Cause:

The module has been removed or is not detected.



Remedy:


  • Ensure Solutions Module is installed correctly.

  • Reinstall Solutions Module.

  • Save parameters and reset drive.
SL.rtd

Solutions Module trip: Drive mode has changed and Solutions Module parameter routing is now incorrect
Cause:

Drive mode change resulted in invalid parameter routing.



Remedy:


  • Press reset.

  • If the trip persists, contact the supplier of the drive.
SLX.tO

Solutions Module slot X trip: Solutions Module watchdog timeout
Cause:

Watchdog timeout occurred on the module.



Remedy:


  • Press reset.

  • If the trip persists, contact the supplier of the drive.
t038

User trip defined in 2nd processor Solutions Module code
Cause:

User-defined trip triggered by SM-Applications.



Remedy:


  • SM-Applications program must be interrogated to find the cause of this trip.
t040 to t089

User trip defined in 2nd processor Solutions Module code
Cause:

User-defined trip triggered by SM-Applications.



Remedy:


  • SM-Applications program must be interrogated to find the cause of this trip.
t099

User trip defined in 2nd processor Solutions Module code
Cause:

User-defined trip triggered by SM-Applications.



Remedy:


  • SM-Applications program must be interrogated to find the cause of this trip.
t101

User trip defined in 2nd processor Solutions Module code
Cause:

User-defined trip triggered by SM-Applications.



Remedy:


  • SM-Applications program must be interrogated to find the cause of this trip.
t112 to t160

User trip defined in 2nd processor Solutions Module code
Cause:

User-defined trip triggered by SM-Applications.



Remedy:


  • SM-Applications program must be interrogated to find the cause of this trip.
t168 to t174

User trip defined in 2nd processor Solutions Module code
Cause:

User-defined trip triggered by SM-Applications.



Remedy:


  • SM-Applications program must be interrogated to find the cause of this trip.
t216

User trip defined in 2nd processor Solutions Module code
Cause:

User-defined trip triggered by SM-Applications.



Remedy:


  • SM-Applications program must be interrogated to find the cause of this trip.
th

Motor thermistor trip
Cause:

Motor over-temperature detected.



Remedy:


  • Check motor temperature.

  • Check thermistor continuity.

  • Set Pr 7.15 = VOLt and reset the drive to disable this function.
thS

Motor thermistor short circuit
Cause:

Short circuit detected in thermistor 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 before completion
Cause:

The drive has tripped out during the autotune, the red stop key was pressed, or SAFE TORQUE OFF (SECURE DISABLE) signal was active.



Remedy:


  • Check stop key status and enable signals (terminal 31).
tunE1*

The position feedback did not change or required speed could not be reached during the inertia test
Cause:

Motor shaft locked or parameters incorrect.



Remedy:


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

  • Ensure Pr 3.26 and Pr 3.38 are set correctly.

  • Check feedback device wiring is correct.

  • Check encoder coupling to motor.
tunE2*

Position feedback direction incorrect or motor could not be stopped during the inertia test
Cause:

Incorrect phasing or wiring.



Remedy:


  • Check motor cable wiring is correct.

  • Check feedback device wiring is correct.

  • Swap any two motor phases.
tunE3*

Drive encoder commutation signals connected incorrectly or measured inertia out of range
Cause:

Commutation signal wiring issue.



Remedy:


  • Check motor cable wiring is correct.

  • Check feedback device U,V and W commutation signal wiring is correct.
tunE4*

Drive encoder U commutation signal fail during an autotune
Cause:

U phase signal loss.



Remedy:


  • Check feedback device U phase commutation wires continuity.

  • Replace encoder.
tunE5*

Drive encoder V commutation signal fail during an autotune
Cause:

V phase signal loss.



Remedy:


  • Check feedback device V phase commutation wires continuity.

  • Replace encoder.
tunE6*

Drive encoder W commutation signal fail during an autotune
Cause:

W phase signal loss.



Remedy:


  • Check feedback device W phase commutation wires continuity.

  • Replace encoder.
tunE7*

Motor number of poles set incorrectly
Cause:

Incorrect pole configuration detected.



Remedy:


  • Check lines per revolution for feedback device.

  • Check the number of poles in Pr 5.11 is set correctly.
Unid.P

Power module unidentified trip
Cause:

Communication or noise issue with power modules.



Remedy:


  • Check all interconnecting cables between power modules.

  • Ensure cables are routed away from electrical noise sources.
UP ACC

Onboard PLC program: cannot access Onboard PLC program file on drive
Cause:

Disable drive – write access is not allowed when the drive is enabled. Another source is already accessing Onboard PLC program.



Remedy:


  • Retry once other action is complete.
UP div0

Onboard PLC program attempted divide by zero
Cause:

Logic error in program.



Remedy:


  • Check program.
UP OFL

Onboard PLC program variables and function block calls using more than the allowed RAM space (stack overflow)
Cause:

Stack overflow.



Remedy:


  • Check program.
UP ovr

Onboard PLC program attempted out of range parameter write
Cause:

Writing value outside allowed range.



Remedy:


  • Check program.
UP PAr

Onboard PLC program attempted access to a non-existent parameter
Cause:

Parameter does not exist.



Remedy:


  • Check program.
UP ro

Onboard PLC program attempted write to a read-only parameter
Cause:

Illegal write operation.



Remedy:


  • Check program.
UP So

Onboard PLC program attempted read of a write-only parameter
Cause:

Illegal read operation.



Remedy:


  • Check program.
UP udF

Onboard PLC program un-defined trip
Cause:

Undefined trip instruction.



Remedy:


  • Check program.
UP uSEr

Onboard PLC program requested a trip
Cause:

Program requested trip.



Remedy:


  • Check program.
UV

DC bus under voltage threshold reached
Cause:

DC Bus voltage dropped below the threshold (e.g., 175V for 200V drive, 330V for 400V drive).



Remedy:


  • Check AC supply voltage level.

  • Verify Drive voltage rating matches supply.
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:

Reduce braking energy or check braking resistor sizing.
Hot
Heatsink or control board over temperature
Cause:

Heatsink or control board or inverter IGBT over temperature alarms are active:

  • The drive heatsink temperature has reached a threshold and the drive will trip O.ht2 if the temperature continues to rise.

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





Remedy:

Check cabinet ventilation, fans, and 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 or check motor sizing.
Auto tune
Autotune in progress
Cause:

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



Remedy:

Wait for the autotune process 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 switch status and machine position.
PLC
Onboard PLC program is running
Cause:

An Onboard PLC program is installed and running. The lower display will flash ‘PLC’ once every 10s.



Remedy:

None (Normal operation).
ACt
Regeneration mode active
Cause:

The regen unit is enabled and synchronised to the supply. (Drive output stage: Enabled).



Remedy:

None (Normal operation).
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. (Drive output stage: Enabled).



Remedy:

Check main AC power supply.
dc
DC applied to the motor
Cause:

The drive is applying DC injection braking. (Drive output stage: Enabled).



Remedy:

None (Normal operation).
dEC
Decelerating
Cause:

The drive is decelerating the motor. (Drive output stage: Enabled).



Remedy:

None (Normal operation).
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. (Drive output stage: Disabled).



Remedy:

Check Enable signal on terminal 31 or parameter 6.15.
POS
Positioning
Cause:

The drive is positioning/orientating the motor shaft. (Drive output stage: Enabled).



Remedy:

None (Normal operation).
rdY
Ready
Cause:

The drive is ready to be run. (Drive output stage: Disabled).



Remedy:

Apply run command to start.
run
Running
Cause:

The drive is running. (Drive output stage: Enabled).



Remedy:

None (Normal operation).
SCAn
Scanning
Cause:

Regen > The drive is enabled and is synchronising to the line. (Drive output stage: Enabled).



Remedy:

Wait for synchronization.
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. (Drive output stage: Enabled).



Remedy:

Check run/stop commands or line voltage if in Regen mode.
triP
Trip condition
Cause:

The drive has tripped and is no longer controlling the motor. The trip code appears on the lower display. (Drive output stage: Disabled).



Remedy:

Investigate the specific trip code shown on the lower display.
boot
Booting / Transfer
Cause:

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



Remedy:

Refer to section 9.2.4 “Booting up from the SMARTCARD on every power up” (Pr 11.42 = boot (4)).
cArd
Writing to Card
Cause:

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



Remedy:

Refer to section 9.2.3 “Auto saving parameter changes” (Pr 11.42 = Auto (3)).
loAding
Loading to Module
Cause:

The drive is writing information to a Solutions Module.



Remedy:

Wait for the process to complete.

Critical Note: If the drive displays a code starting with “HF” (e.g., HF08), this indicates a Hardware Fault. These are internal failures (like power stage or processor errors) and typically require professional repair or replacement of the drive.

How to Read Unidrive SP Faults via CTSoft

In 2026, the most effective way to troubleshoot an aging Unidrive SP is by using the legacy CTSoft software tool or the newer Connect software (which supports the SP via a serial connection).

  • SM-Option Modules: The Unidrive SP has three slots for SM-Option modules (e.g., SM-Encoder, SM-Ethernet). If a trip occurs related to a module, the drive will often display a sub-trip code to identify which slot (1, 2, or 3) caused the issue.
  • Trip History (Menu 10): The drive stores the last 10 trips in Parameters 10.20 through 10.29.
    • 10.20: The most recent trip.
    • 10.21 – 10.29: The previous 9 trips.
  • SmartStick: If the drive is equipped with a SmartStick (the green memory stick), fault logs and parameter sets can be easily cloned or transferred to a replacement drive, which is a common practice for maintaining legacy systems in 2026.
  • CTSoft Monitoring: By connecting a PC via an RS485 lead (CT-USB-Cable), you can monitor the DC bus voltage and output current in real-time, which is essential for catching “nuisance” OV (Overvoltage) trips.

Frequently Asked Questions (FAQ)

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

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

Q: How do I reset a Unidrive SP trip?

A: After the cause of the fault has been cleared, you can reset the drive by:

  • Pressing the Red Reset Button on the keypad.
  • Toggling a Digital Input assigned to the “Reset” function (Terminal 31 is often used).
  • Cycling the Main Power (Wait 30 seconds for the display to go completely dark before turning it back on).

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

A: “ih” stands for Inhibit. This is not a fault; it is a status. 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: Where is the trip history stored?

A: Trip history is stored in the non-volatile memory of the drive in Menu 10. Even if the drive is powered down for years, the log of the last 10 trips remains available for technicians to review.

Q: My drive shows “OI.AC,” what is the first thing to check?

A: OI.AC stands for Overcurrent (AC). The most common cause is a short circuit in the motor cables or a grounded motor winding. Disconnect the motor cables from the drive and see if the trip clears; if the drive still trips with the motor disconnected, the internal power stage has failed.