Hitachi WJ-C1 Fault Codes & Troubleshooting List 2026

Categories: Drives, PLC & HMI, Faults & Alarm

Hitachi WJ-C1 Fault Codes & Troubleshooting List 2026 – Troubleshoot your Hitachi WJ-C1 compact inverter with our updated 2026 guide. Learn to interpret E01-E60 trips, use ProDriveNext diagnostics, and reset faults to minimize downtime.

The Hitachi WJ-C1 is a compact, space-saving inverter designed for versatile industrial applications. It combines ease of use with robust protective functions. When the drive detects an anomaly—whether it’s an electrical surge or a mechanical overload—the 4-digit LED display on the front panel will flash a trip code starting with “E” (e.g., E01, E07, E09).

This guide provides the most up-to-date resources for 2026 to help you interpret these codes and restore your production line efficiently.

WJ-C1 Fault Codes Reference Table

Below is the complete list of protective functions and alarm codes for the WJ-C1. Please refer to this table to match the alphanumeric code on your display with the specific diagnostic remedy.

Fault Code and MeaningCause and Remedy
E01.*

Over current error (Constant speed)
Cause:

  • Is there a steep load change?

  • Is there an output short circuit?

  • Is there a ground fault?




Remedy:

  • Eliminate load fluctuation.

  • Check the output line.

  • Check the output wires and motor.
E02.*

Over current error (During deceleration)
Cause: Rapid deceleration.



Remedy:

  • Increase the deceleration time.
E03.*

Over current error (During acceleration)
Cause:

  • Rapid acceleration.

  • Is motor locked?

  • Is the torque boost high?




Remedy:

  • Increase the acceleration time.

  • Check the motor and wiring.

  • Decrease the boost value.
E04.*

Over current error (Other)
Cause: Is DC braking high?



Remedy:

  • Decrease the DC braking force.
E05.*

Overload error
Cause:

  • Is the acceleration torque insufficient?

  • Is the load too heavy?

  • Is thermal level correct?




Remedy:

  • Increase the acceleration time.

  • Lower the load factor.

  • Set to the proper level.
E06.*

Braking resistor overload error
Cause:

  • Is it decelerating rapidly?

  • Is the operation cycle short?




Remedy:

  • Increase the deceleration time.

  • Increase the operating cycle.
E07.*

Overvoltage error
Cause:

  • Is it decelerating rapidly?

  • Is there a ground fault?

  • Is the motor rotated from the load side?

  • Is the power supply voltage rising?




Remedy:

  • Increase the deceleration time.

  • Check the output wires and motor.

  • Reduce the regeneration amount.

  • Lower the power supply voltage, suppress power fluctuations, or insert an AC reactor into the input.
E08.*

Memory error
Cause:

  • Is there a large noise source nearby?

  • Is the cooling efficiency lowered?




Remedy:

  • Noise suppression.

  • Check for clogging of the cooling fins and clean it, and replace the cooling fans.
E09.*

Undervoltage error
Cause:

  • Power supply voltage is not dropped?

  • Is the power supply capacity insufficient?

  • Is there any aging degradation of the smoothing capacitor?




Remedy:

  • Check the power supply.

  • See “Smoothing Capacitor Life Curve”.
E10.*

Current detector error
Cause: Inverter failure.



Remedy:

  • Repair.
E11.*

CPU error
Cause:

  • Is there a large noise source nearby?

  • Inverter failure.




Remedy:

  • Noise suppression.

  • Repair.
E12.*

External trip error
Cause:

  • Is input signal normal?

  • Is there a large noise source nearby?




Remedy:

  • Check the external input device and wiring.

  • Noise suppression.
E13.*

USP error
Cause: Is the power supply turned on with the RUN command input?



Remedy:

  • Check the operation signal.
E14.*

Ground fault
Cause:

  • Is there a ground fault?

  • Is there any abnormality in the inverter alone?

  • Is there any abnormality in the main circuit part?




Remedy:

  • Check the output wires and motor.

  • Disconnect and check the output wires.

  • Check the main circuit. (Refer to “Daily Inspection and Periodic Inspection”).
E15.*

Power supply overvoltage error
Cause: Is the power supply voltage too high?



Remedy:

  • Decrease the power supply voltage.

  • Suppress power supply fluctuations.

  • Insert an AC reactor into the input.
E19.*

Temperature detection error
Cause: Inverter failure.



Remedy:

  • Repair.
E21.*

Cooling fin temperature error
Cause:

  • Is the inverter mounted vertically?

  • Is the ambient temperature too high?

  • Is the cooling fan not stopped?

  • Is the cooling fin clogged?




Remedy:

  • Check the installation.

  • Lower the temperature.

  • Set “Cooling fan control method selection [b092]” to “Always (00)” and check fan power supply.

  • Clean the fin.
E22.*

CPU communication error
Cause:

  • Is there a large noise source nearby?

  • Inverter failure.




Remedy:

  • Noise suppression.

  • Repair.
E25.*

Main circuit error
Cause:

  • Is there a large noise source nearby?

  • Inverter failure.




Remedy:

  • Noise suppression.

  • Repair.
E26.*

Analog current input error
Cause:

  • Is [Ai2] wiring short-circuited or incorrect wiring?

  • Control circuit board failure.




Remedy:

  • Check the wiring.

  • Repair.
E30.*

Driver error
Cause:

  • Is there an output short circuit?

  • Is there a ground fault?

  • Is there any damage to the main element?




Remedy:

  • Check the output line.

  • Check the output wires and motor.

  • Checking IGBT (See “Checking the Inverter and Converter Section”).
E35.*

Thermistor error (Motor temperature error)
Cause:

  • Is the motor temperature too high?

  • Is there any damage to the thermistor?

  • Is there noise contamination to the thermistor signal?




Remedy:

  • Check the temperature.

  • Check the thermistor.

  • Wiring separation.
E36.*

Brake error
Cause:

  • Is ON/OFF operation of the braking normal?

  • Is the setting of [b124] too short?

  • Is the “Answer back from Brake [BOK]” signal turned on?




Remedy:

  • Check the brake.

  • Increase the [b124].

  • Check wiring.
E37.*

STO shut-off error
Cause:

  • Is [ST1]/[ST2] incorrectly input?

  • Is parameter setting correct?




Remedy:

  • Check the wiring and sequence of [ST1]/[ST2] input signals.

  • Check the [b145] setting.
E38.*

Low-speed range overload error
Cause: Is the load too heavy?



Remedy:

  • Lower the load factor.
E40.*

Remote operator communication error
Cause: Is there a communication error?



Remedy:

  • Check/replace the cable.
E41.*

Modbus communication error
Cause:

  • Is the settings of communication baud rate etc. correct?

  • Are the length and shield of the wirings appropriate? Also, are wires not broken?

  • Is the termination resistor setting correct?




Remedy:

  • Check the settings.

  • Check the communication wiring.

  • Check the termination resistor.
E43.*

EzSQ invalid instruction error
Cause: Invalid instruction detected in EzSQ program.



Remedy:

  • Refer to “Inverter configuration software ProDriveNext instruction manual”.
E44.*

EzSQ nesting count error
Cause: Nesting count exceeds allowable executed number.



Remedy:

  • Refer to “Easy-Sequence Function (EzSQ) Programming Guide”.
E45.*

EzSQ execution error
Cause: Instruction that cannot be executed is detected.



Remedy:

  • Refer to EzSQ Programming Guide.
E50.* to E59.*

EzSQ user-assigned error 0 to 9
Cause: Corresponding user-assigned tripping programs executed in EzSQ.



Remedy:

  • Check user program logic.
E60.* to E69.*

Option related error
Cause:

  • Is the option board connected properly?

  • Is there a mistake in usage?




Remedy:

  • Check connector fitting.

  • Check the instruction manual for the option.
E80.*

Encoder disconnection error
Cause:

  • Are there any broken or faulty connections in the encoder wiring?

  • Are the parameter settings correct?




Remedy:

  • Check the encoder wiring.

  • Increase [P077] and set [P015] to a higher value.
E81.*

Overspeed error
Cause:

  • Are there any broken or faulty connections in the encoder wiring?

  • Are the parameter settings correct?

  • Is the actual motor speed higher than the error detection level?




Remedy:

  • Check the encoder wiring.

  • Check “Output frequency setting or monitor [F001]” and Encoder constant [P011].

  • Check the load status and adjust [P026].
E83.*

Position control range error
Cause: Is the current position and home position correct?



Remedy:

  • Check [P072] and [P073].

  • Check [P060] to [P067].

  • Check the home position.
E98.*

ST1/ST2 mismatch error
Cause:

  • Is [ST1]/[ST2] incorrectly input?

  • Is parameter setting correct?




Remedy:

  • Check [ST1]/[ST2] input signal wiring and perform function tests.

  • Check the [b145] setting.
E99.*

STO internal failure error
Cause: Is the safety function working properly?



Remedy:

  • Perform function tests.

  • Failure in the internal safety path -> Repair.

How to Read WJ-C1 Faults via ProDriveNext

While the integrated keypad is sufficient for basic identification, connecting your PC to the WJ-C1 using ProDriveNext software provides professional-grade diagnostic data for 2026 maintenance standards.

  • Fault History (d081 to d086): The WJ-C1 records the last 6 trip events. You can access these via the keypad by navigating to the Monitor (d) group. Parameter d081 displays the most recent fault.
  • Trip Status Details: When viewing a trip in d081, the display alternates between the fault code and the electrical status of the drive at the moment of failure, including output frequency, motor current, and DC bus voltage.
  • Software Trace: ProDriveNext allows you to view the “Fault Monitor” window, which graphs the current and voltage leading up to a trip, making it easier to identify if a E01 (Overcurrent) trip was caused by a mechanical jam or a logic error.

General Troubleshooting Steps

Before performing a manual reset on your Hitachi WJ-C1, perform these essential hardware checks:

  1. Overcurrent (E01 – E04): Check for short circuits in the motor wiring. If the trip happens during acceleration, try increasing the Acceleration Time (Parameter F002) or checking for mechanical binding on the motor shaft.
  2. Overvoltage (E07): This usually occurs during rapid deceleration of a high-inertia load. Increase the Deceleration Time (Parameter F003) or check the input AC line for voltage spikes.
  3. Under-voltage (E09): Check the stability of your power supply. This trip is common in facilities where the power sags when larger machinery starts up on the same circuit.

Frequently Asked Questions (FAQ)

Q: How do I reset a fault on the Hitachi WJ-C1?

A: Once the cause of the trip is resolved, you can reset the drive using one of these methods:

  • Press the Stop/Reset key on the front keypad.
  • Activate the digital input terminal assigned to the RS (Reset) function (Terminal 4 or 5 depending on setup).
  • Cycle the main input power (Wait until the display goes completely dark before turning the power back on).

Q: What is the “USP” error on my Hitachi WJ-C1?

A: USP (Unattended Start Protection) is a safety feature. It prevents the motor from starting automatically if the Run command is already active when you power up the drive. Simply turn the Run command OFF to clear the message.

Q: Why does my drive show “E14” (Ground Fault)?

A: E14 indicates that current is leaking to the earth on the output side. This is often caused by damaged motor insulation or moisture in the conduit. Do not ignore this trip, as it can cause damage to the drive’s internal power modules.

Q: Where is the fault history stored?

A: You can find the history of the last 6 faults in the Monitor (d-group), specifically parameters d081 through d086. Each entry provides a snapshot of the inverter’s electrical data at the time of the error.