Access the complete list of Mitsubishi FR-CS80 fault codes (E.OC1, E.OV1, etc.). Learn to troubleshoot trips, use FR Configurator2, and minimize downtime.

Mitsubishi FR-CS80 Fault Codes Reference Table (2026)

Below is the complete troubleshooting list for identifying specific drive issues.

Mitsubishi FR-CS80 Fault Codes List

Fault Code and Meaning	Cause and Remedy
HOLD Operation panel lock	Cause: Operation lock is set. Operation other than STOP/RESET is invalid. Remedy: Press MODE for 2 seconds to release the lock.
LOCD Parameter locked	Cause: Password function is active. Display and setting of parameters are restricted. Remedy: Enter the password in Pr.297 (Password lock/unlock) to unlock the password function before the operation.
Er1 Write disable error	Cause: Parameter setting was attempted while Pr.77 is set to disable write, or overlapping ranges set for frequency jump/adjustable 5 points V/F. The PU and inverter may not be communicating normally. Remedy: Check the Pr.77 Parameter write selection setting. Check the settings of Pr.31 to Pr.36 (frequency jump). Check the settings of Pr.100 to Pr.105 (adjustable 3 points V/F). Check the connection of the PU and the inverter.
Er2 Write error during operation	Cause: Parameter write was attempted while Pr.77 Parameter write selection = "0". Remedy: Check that the inverter is stopped. After stopping the operation, make parameter setting. When setting Pr.77 = "2", parameter write is enabled during operation.
Er3 Calibration error	Cause: Analog input bias and gain calibration values are set too close. Remedy: Check the settings of the calibration parameters C3, C4, C6, and C7 (calibration functions).
Er4 Mode designation error	Cause: Parameter setting is attempted in the External or NET operation mode when Pr.77 = "1", or when the command source is not at the operation panel. Remedy: Check that operation mode is PU operation mode. Check that the Pr.551 PU mode operation command source selection setting is correct. After setting the operation mode to the "PU operation mode", set the parameter. When Pr.77 = "2", parameter write is enabled regardless of the operation mode.
Err. (Error)	Cause: The RES signal is turned ON, or voltage at the input side of the inverter has dropped. Remedy: Turn OFF the RES signal. Check the voltage on the input side of the inverter.
OLC (FR-LU08: OL) Stall prevention (overcurrent)	Cause: When the output current of the inverter increases, the stall prevention function is activated. This stops the increase (during accel) or decreases frequency (during constant speed/decel) to prevent an overcurrent trip. Remedy: Check that the Pr.0 Torque boost setting is not too large. Check if Pr.7 Acceleration time and Pr.8 Deceleration time settings are too short. Check that the load is not too heavy. Check for any failures in peripheral devices. Check that Pr.13 Starting frequency is not too large. Check that Pr.22 Stall prevention operation level is appropriate. Set a larger value in Pr.7 and Pr.8. Reduce the load or try General-purpose magnetic flux vector control.
OLV (FR-LU08: oL) Stall prevention (overvoltage)	Cause: When the output voltage increases, the stall prevention function is activated. The regeneration avoidance function may be activated due to excessive regenerative power. Remedy: Check for sudden speed reduction. Check if the regeneration avoidance function (Pr.882, Pr.883, etc.) is enabled. Increase the deceleration time using Pr.8 Deceleration time.
TH Electronic thermal O/L relay pre-alarm	Cause: Appears if the cumulative value of the electronic thermal O/L relay reaches 85% of the preset level of Pr.9. Remedy: Check for large load or sudden acceleration. Check that the Pr.9 setting is appropriate. Reduce the load and frequency of operation. Set an appropriate value in Pr.9.
PS PU stop	Cause: The motor is stopped using STOP/RESET under a mode other than PU operation mode (if Pr.75 is set to allow this), or by the emergency stop function. Remedy: Check if the motor is stopped by pressing STOP/RESET on the operation panel. Turn OFF the start signal and switch the operation mode to the PU operation mode to reset.
UV Undervoltage	Cause: Power supply voltage of the inverter decreased to about 115 VAC (200V class) or 230 VAC (400V class) or below. Remedy: Check that the power supply voltage is appropriate. Check if a high-capacity motor is driven. Investigate the devices on the power supply line such as the power supply itself.
IH Inrush current limit resistor overheat	Cause: The inrush current limit resistor (PTC thermistor) is overheated due to frequent power ON/OFF cycling. Remedy: Check that power ON/OFF is not repeated frequently. Check that the inrush current limit circuit is not damaged. Configure a circuit where frequent power ON/OFF is not repeated. If problem persists, contact your sales representative.
ED Emergency drive in operation	Cause: Emergency drive operation is performed by turning ON the X84 signal. Remedy: The display is cleared when the emergency drive operation ends.
E.OC1 Overcurrent trip during acceleration	Cause: Check for sudden speed acceleration. Check if the downward acceleration time is too long in a lift application. Check for output short-circuit. Check that the Pr.3 Base frequency setting is not 60 Hz when the motor rated frequency is 50 Hz. Check if the stall prevention operation level is set too high. Check if the fast-response current limit operation is disabled. Check that the regenerative driving is not performed frequently. Remedy: Set the acceleration time longer. (Shorten the downward acceleration time of the lift.) If "E.OC1" always appears at start, disconnect the motor once and restart the inverter. If it still appears, contact your sales representative. Check the wiring to make sure that output short circuit does not occur. Set 50 Hz in Pr.3 Base frequency. Lower the stall prevention operation level. Activate the fast-response current limit operation. Set the base voltage in Pr.19 Base frequency voltage.
E.OC2 Overcurrent trip during constant speed	Cause: Check for sudden load change. Check for output short-circuit. Check if the stall prevention operation level is set too high. Check if the fast-response current limit operation is disabled. Remedy: Keep the load stable. Check the wiring to make sure that output short circuit does not occur. Lower the stall prevention operation level. Activate the fast-response current limit operation.
E.OC3 Overcurrent trip during deceleration or stop	Cause: Check for sudden speed reduction. Check for output short-circuit. Check for too fast operation of the motor's mechanical brake. Check if the stall prevention operation level is set too high. Check if the fast-response current limit operation is disabled. Remedy: Set the deceleration time longer. Check the wiring to make sure that output short circuit does not occur. Check the mechanical brake operation. Lower the stall prevention operation level. Activate the fast-response current limit operation.
E.OV1 Regenerative overvoltage trip during acceleration	Cause: Check for too slow acceleration. (e.g. during downward acceleration in vertical lift load) Check that the Pr.22 Stall prevention operation level is not set to the no load current or lower. Check if the stall prevention operation is frequently activated in an application with a large load inertia. Remedy: Set the acceleration time shorter. Use the regeneration avoidance function (Pr.882, Pr.883, Pr.885, Pr.886). Set a value larger than the no load current in Pr.22.
E.OV2 Regenerative overvoltage trip during constant speed	Cause: Check for sudden load change. Check that the Pr.22 Stall prevention operation level is not set to the no load current or lower. Check if the stall prevention operation is frequently activated in an application with a large load inertia. Check that acceleration/deceleration time is not too short. Remedy: Keep the load stable. Use the regeneration avoidance function (Pr.882, Pr.883, Pr.885, Pr.886). Use a brake unit or the power regeneration common converter (FR-CV) as required. Set a value larger than the no load current in Pr.22. Set the acceleration/deceleration time longer.
E.OV3 Regenerative overvoltage trip during deceleration or stop	Cause: Check for sudden speed reduction. Check if the stall prevention operation is frequently activated in an application with a large load inertia. Remedy: Set the deceleration time longer. (Set the deceleration time which matches the moment of inertia of the load.) Make the brake cycle longer. Use the regeneration avoidance function (Pr.882, Pr.883, Pr.885, Pr.886). Use the brake unit or power regeneration common converter (FR-CV) as required. Enable the increased magnetic excitation deceleration.
E.THT Inverter overload trip (electronic thermal O/L relay function)	Cause: Check that acceleration/deceleration time is not too short. Check that torque boost setting is not too large (small). Check that load pattern selection setting is appropriate for the load pattern of the machine. Check that the motor is not used under overload. Remedy: Set the acceleration/deceleration time longer. Adjust the torque boost setting. Set the load pattern selection setting according to the load pattern of the using machine. Reduce the load.
E.THM Motor overload trip (electronic thermal O/L relay function)	Cause: Check if the motor is not used under overload. Check that the setting of Pr.71 Applied motor for motor selection is correct. Check that the stall prevention operation setting is correct. Remedy: Reduce the load. For a constant-torque motor, set the constant-torque motor in Pr.71 Applied motor. Set the stall prevention operation level accordingly.
E.FIN Heatsink overheat	Cause: Check for too high surrounding air temperature. Check for heat sink clogging. Check that the cooling system is not stopped. Remedy: Set the surrounding air temperature to within the specifications. Clean the heatsink. If the problem still persists after taking the above measure, contact your sales representative.
E.UVT Undervoltage	Cause: Check if a high-capacity motor is driven. Remedy: Check the devices on the power supply line such as the power supply itself. If the problem still persists after taking the above measure, contact your sales representative.
E.ILF Input phase loss	Cause: Check if a high-capacity motor is driven. Check that phase-to-phase voltage of the three-phase power input is not largely unbalanced. Remedy: Wire the cables properly. Check the Pr.872 setting.
E.OLT Stall prevention stop	Cause: Output frequency has fallen to 1 Hz by stall prevention operation and remains for 3 seconds. Check if the motor is not used under overload. Remedy: Reduce the load. Change the Pr.22 setting. Check that stall prevention (overcurrent) warning (OLC) or stall prevention (overvoltage) warning (OLV) countermeasure is taken.
E.GF Output side earth (ground) fault overcurrent	Cause: Earth (ground) fault overcurrent flows due to an earth fault on the inverter's output side. Check for a ground fault in the motor and connection cable. Remedy: Remedy the earth (ground) fault portion. Check the Pr.249 setting.
E.LF Output phase loss	Cause: One of the three phases (U, V, W) on the inverter's output side is lost. Check wiring and that motor capacity is not smaller than inverter. Remedy: Wire the cables properly. Check the Pr.251 setting.
E.OHT External thermal relay operation	Cause: External or internal thermal relay switches ON (contacts open). Check for motor overheating. Check Pr.178 to Pr.182 settings. Remedy: Reduce the load and operation duty. Even if relay contacts reset automatically, the inverter will not restart unless reset manually.
E.PE6 Internal storage device fault	Cause: Writing data failed due to power-OFF or data fault during parameter operations. Check if power was turned OFF during operations. Remedy: Check power supply and devices. If due to power-OFF: Check Pr.890. If "7" or smaller, perform All parameter clear and reset. If due to other reasons: Contact sales representative.
E.PE / E.PE2 Parameter storage device fault (Corrupt Memory)	Cause: A fault occurred in the stored parameters (EEPROM failure). Check for too many parameter write times. Remedy: Contact your sales representative. If writing frequently for communication, set "1" in Pr.342 to enable RAM write.
E.PUE PU disconnection	Cause: Communication between inverter and PU is suspended/disconnected. Check that PU is connected properly and Check Pr.75. Remedy: Connect the PU securely.
E.RET Retry count excess	Cause: Operation cannot be resumed properly within the number of retries set in Pr.67. Find the cause of the fault occurrence. Remedy: Eliminate the cause of the fault preceding this fault indication.
E.CPU / E.5 CPU fault	Cause: Communication fault of the built-in CPU. Check for devices producing excess electrical noises around the inverter. Remedy: Take measures against noises if there are devices producing excess electrical noises. Contact your sales representative.
E.CDO Abnormal output current detection	Cause: Output current exceeds Pr.150 level. Check settings of Pr.150, Pr.151, and Pr.167. Remedy: Adjust the parameter settings (Pr.150, Pr.151, Pr.167) or load conditions.
E.IOH Inrush current limit circuit fault	Cause: Resistor of inrush current limit circuit is overheated or faulty. Check that frequent power ON/OFF is not repeated. Remedy: Configure a circuit where frequent power ON/OFF is not repeated. If problem persists, contact sales representative.
E.ICF Input monitoring fault	Cause: Input signal does not turn ON/OFF within time set in Pr.242. Check for input signal loss or device failure. Remedy: Set the Pr.242 setting larger. Check connection of input devices.
E.LCI 4 mA input fault	Cause: Analog input current is 2 mA or less. Check for break in wiring or Pr.778 setting. Remedy: Check the wiring for the analog current input. Set the Pr.778 setting larger.
E.E10 Inverter output fault	Cause: Fault on inverter output side while Pr.631 is active. Check for ground fault in motor/cable. Remedy: Remedy the earth (ground) fault portion. Check the Pr.631 setting.
E.0 No fault history	Cause: Appears when no fault records are stored. Remedy: None required (System Normal).

 

How to Read FR-CS80 Faults via FR Configurator2

To get the most accurate diagnostic data in 2026, it is highly recommended to connect your PC to the drive using the FR Configurator2 software via a USB or RS-485 connection. This software offers advanced troubleshooting features:

• Alarm History: View the detailed history of the last 8 alarms, including output frequency, current, and voltage at the time of the trip.
• Graph Function: Monitor real-time data to identify load spikes or irregularities before they cause a hard fault.
• Diagnosis Mode: Quickly check the status of I/O signals and internal inverter thermal load to pinpoint hardware issues.

Frequently Asked Questions (FAQ)

Q: What is the difference between a Warning and a Fault?
A: A Warning (codes like ‘OL’, ‘PS’, ‘TH’) indicates an abnormal condition—such as an overload or panel lock—but typically keeps the motor running. A Fault (codes starting with ‘E.’, like ‘E.OC1’) triggers the protective function, shutting off the inverter output and stopping the motor immediately.

Q: How do I reset a Mitsubishi FR-CS80 fault?
A: You can reset a fault by pressing the STOP/RESET button on the operation panel, switching the power supply OFF and ON again, or by turning on the RES (Reset) signal terminal.

Q: Where is the fault history stored?
A: The FR-CS80 stores the last 8 fault records. You can view these directly on the operation panel by pressing the MODE button until the “Fault History” screen appears, or by using the FR Configurator2 software to read the drive’s internal memory.