Hitachi S1 Fault Codes & Troubleshooting List 2026 – Troubleshoot your Hitachi S1 high-performance inverter with our updated 2026 guide. Learn to interpret E001-E100 trips, use the LCD keypad for diagnostics, and reset faults.
The Hitachi S1 is a premier high-performance industrial inverter designed for heavy-duty applications requiring precise motor control and high starting torque. In 2026, it is widely utilized in global automation systems for its advanced sensorless vector control. When the drive encounters a protective limit, it displays an alphanumeric error code (e.g., E001, E007, E014) on its high-definition LCD keypad.
This guide provides the most updated resources for 2026 to help you diagnose these error codes and restore your high-capacity industrial systems quickly.
Hitachi S1 Fault Codes Reference Table
Below is the reference for the Hitachi S1 protective functions. Match the “E” code appearing on your LCD operator with the diagnostic table below to identify the root cause of the shutdown.
| Fault Code and Meaning | Cause and Remedy |
|---|---|
| OUt1 Inverter unit Phase-U protection | Cause: Acceleration is too fast; IGBT module is damaged; Misacts caused by interference; drive wires are poorly connected. Remedy:
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| OUt2 Inverter unit Phase-V protection | Cause: Acceleration is too fast; IGBT module is damaged; Misacts caused by interference; drive wires are poorly connected. Remedy:
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| OUt3 Inverter unit Phase-W protection | Cause: To-ground short circuit occurs; IGBT module damage; Interference. Remedy:
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| OV1 Over-voltage during acceleration | Cause: Exception occurred to input voltage; Large energy feedback; Lack of brake units; Dynamic brake is not enabled. Remedy:
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| OV2 Over-voltage during deceleration | Cause: Exception occurred to input voltage; Large energy feedback; Lack of brake units. Remedy:
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| OV3 Over-voltage during constant speed running | Cause: Exception occurred to input voltage; Large energy feedback; Dynamic brake is not enabled. Remedy:
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| OC1 Over-current during acceleration | Cause: Acceleration is too fast; Grid voltage is too low; Inverter power is too small; Load transient or exception occurred. Remedy:
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| OC2 Over-current during deceleration | Cause: Deceleration is too fast; Load transient; Inverter power is too small. Remedy:
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| OC3 Over-current during constant speed running | Cause: Load transient; To-ground short circuit or output phase loss occur; Strong external interference sources; Overvoltage stall protection is not enabled. Remedy:
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| UV Bus undervoltage fault | Cause: Grid voltage is too low; Overvoltage stall protection is not enabled. Remedy:
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| OL1 Motor overload | Cause: Grid voltage is too low; Rated motor current is set improperly; Motor stall or load jumps violently. Remedy:
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| OL2 Inverter overload | Cause: Acceleration is too fast; The motor in rotating is restarted; Grid voltage is too low; Load is too large; Power is too small. Remedy:
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| SPI Phase loss on input side | Cause: Phase loss or violent fluctuation occurred to R, S and T input. Remedy:
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| SPO Phase loss on output side | Cause: Phase loss occurred to U, V, W output (or the three phases of motor is asymmetrical). Remedy:
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| OH1 Overheat of rectifier module | Cause: Air duct is blocked or fan is damaged; Ambient temperature is too high; Long-time overload running. Remedy:
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| OH2 Overheat of inverter module | Cause: Air duct blocked; Fan damaged; High ambient temperature; Long-time overload. Remedy:
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| EF External fault | Cause: External fault input terminal acts. Remedy:
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| CE 485 communication fault | Cause: Baud rate is set improperly; Communication line fault; Communication address error; Communication suffers from strong interference. Remedy:
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| ItE Current detection fault | Cause: Poor contact of the connector of control board; Hall component is damaged; Exception occurred to amplification circuit. Remedy:
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| tE Motor autotuning fault | Cause: Motor capacity does not match inverter; Motor parameter set improperly; Autotuning parameters deviate sharply; Autotuning timeout. Remedy:
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| EEP EEPROM fault | Cause: R/W error occurred to the control parameters; EEPROM is damaged. Remedy:
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| PIDE PID feedback offline fault | Cause: PID feedback offline; PID feedback source disappears. Remedy:
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| bCE Brake unit fault | Cause: Brake circuit fault or brake tube is damaged; The resistance of external brake resistor is too small. Remedy:
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| END Running time is up | Cause: The actual running time of the inverter is larger than the set running time. Remedy:
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| OL3 Electronic overload fault | Cause: The inverter releases overload pre-alarm based on the set value. Remedy:
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| PCE Keypad communication fault | Cause: Keypad wire poorly contacted or disconnected; Keypad wire too long/strong interference; Circuit fault to keypad/main board. Remedy:
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| UPE Parameter upload error | Cause: Keypad wire poorly contacted or disconnected; Keypad wire too long/strong interference; Circuit fault. Remedy:
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| DNE Parameter download error | Cause: Keypad wire poorly contacted/disconnected; Keypad wire too long/interference; Data storage error. Remedy:
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| ETH1 To-ground short circuit fault 1 | Cause: Inverter output is short connected to the ground; Current detection circuit is faulty; Actual motor power setup deviates sharply. Remedy:
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| ETH2 To-ground short circuit fault 2 | Cause: Inverter output is short connected to ground; Current detection circuit is faulty; Actual motor power setup deviates sharply. Remedy:
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| LL Electronic underload fault | Cause: The inverter performs underload pre-alarm based on the set value. Remedy:
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| STO Safe torque off | Cause: Safe torque off function is enabled by external forces. Remedy:
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| STL1 Exception occurred to safe circuit of channel H1 | Cause: The wiring of STO is improper; Fault occurred to external switch of STO; Hardware fault occurred to safety circuit of channel H1. Remedy:
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| STL2 Exception occurred to channel H2 safe circuit | Cause: The wiring of STO is improper; Fault occurred to external switch of STO; Hardware fault occurred to safety circuit of channel H2. Remedy:
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| STL3 Exception occurred to channel H1 and channel H2 | Cause: Hardware fault occurred to STO circuit. Remedy:
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| CrCE Safety code FLASH CRC check fault | Cause: Control board is faulty. Remedy:
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| PoFF System power failure | Cause: The system is powered off or the bus voltage is too low. Remedy:
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How to Read S1 Faults via LCD Keypad & ProDriveNext
The Hitachi S1 offers advanced diagnostic visibility compared to previous generations. In 2026, the standard for professional maintenance involves utilizing the LCD interface or Hitachi’s PC software:
- Trip History (d081 to d086): The S1 records the last 6 major trips in its non-volatile memory. Navigate to the Monitor (d) group on the keypad. Parameter d081 stores the most recent fault, including a text description on the LCD.
- Trip Status Snapshot: By selecting a fault in the history, the S1 provides a “snapshot” of the drive’s status. This includes the output frequency, motor current, DC bus voltage, and cumulative power-on time at the exact millisecond of failure.
- ProDriveNext Software: For complex system analysis, connect your PC via the USB port. This software allows you to perform real-time data tracing and parameter comparisons to identify why intermittent E007 (Overvoltage) or E001 (Overcurrent) trips are occurring.
General Troubleshooting Steps
Before performing a manual reset on your Hitachi S1 drive, perform these essential hardware checks:
- Overcurrent (E001 – E004): This indicates an instantaneous spike in current. Check for a short circuit in the motor wiring or a mechanical jam. If this occurs during acceleration, check parameter AC1 (Acceleration Time).
- Overvoltage (E007): Typically occurs when a high-inertia load decelerates too quickly, pushing energy back into the drive. Increase the Deceleration Time (Parameter DE1) or verify that the braking resistor is functioning correctly.
- Ground Fault (E014): The S1 features highly sensitive leakage protection. Check for moisture in the motor terminals or breakdown in cable insulation. Do not ignore this fault, as it can lead to internal IGBT damage.
Frequently Asked Questions (FAQ)
Q: How do I reset a fault on the Hitachi S1?
A: Once the cause of the trip is resolved, you can reset the drive by:
- Pressing the Stop/Reset key on the digital LCD operator.
- Closing the digital input terminal assigned as the RS (Reset) function.
- Cycling the main input power (Wait until the internal capacitors fully discharge before re-applying power).
Q: What is the “USP” error on my Hitachi S1?
A: USP (Unattended Start Protection) is a safety error, not a hardware fault. It occurs if the “Run” command is already active when you power up the drive. Simply turn off the Run signal to clear the display and allow normal operation.
Q: Why does my drive show “E009” (Under-voltage)?
A: E009 means the internal DC bus voltage has dropped below the safety limit. Check your incoming 3-phase power supply for a dropped phase or a significant voltage sag in the factory’s power grid.
Q: Where is the fault history located on the keypad?
A: Navigate to the Monitor Mode (d-group). The history is stored in d081 through d086. Each entry provides a detailed log of the electrical conditions present when the fault occurred.