Complete guide to Mitsubishi FR-XC Regenerative Converter fault codes. Learn to troubleshoot grid connection errors, interpret protection modes, and use FR Configurator2 to maintain power quality.

FR-XC Fault Codes Reference Table

Below is the complete list of fault and warning codes specific to the regenerative converter units. Use the search bar to find specific error codes.

Mitsubishi FR-XC 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.
Er1 Write disable error	Cause: Parameter setting was attempted while Pr.77 Parameter write selection is set to disable parameter write. Remedy: Check the Pr.77 setting.
rE1 Parameter read error	Cause: A failure has occurred at EEPROM in the operation panel during reading of the parameter settings for Parameter copy. Remedy: Perform Parameter copy again. The operation panel (FR-DU08) may be faulty. Contact your sales representative.
rE2 Parameter write error	Cause: Parameter write from the operation panel to the multifunction regeneration converter was attempted for Parameter copy during operation. A failure has occurred at EEPROM in the operation panel during writing of the parameter settings for Parameter copy. Remedy: Check that the converter is stopped. After turning ON the SOF signal, perform Parameter copy again. The operation panel (FR-DU08) may be faulty. Contact your sales representative.
rE3 Parameter verification error	Cause: The data in the converter are different from the data in the operation panel. A failure has occurred at EEPROM in the operation panel during parameter verification. Remedy: Continue the verification by pressing SET. Perform the parameter verification again. The operation panel (FR-DU08) may be faulty. Contact your sales representative.
rE4 Product series error	Cause: The series of the source converter used to copy or verify parameters is not the same as the target converter. The operation panel data was incorrect when attempting to verify parameters or copy parameters from the operation panel to the converter. Remedy: Check that the source converter being used to verify or copy parameters is the same series as the target converter. Check that the copying of parameters was not interrupted due to a loss of power. Try to copy or verify parameters again.
OL / LB Overload signal detection	Cause: Appears when the current limit function of the converter is activated. Remedy: Set the acceleration/deceleration time longer in the inverter. Reduce the load. Check that the peripheral devices are operating properly.
TH / LC Electronic thermal relay function pre-alarm	Cause: Appears if the cumulative value of the electronic thermal relay reaches or exceeds 85% of the preset level. Remedy: Check for large load or sudden acceleration. Reduce the load and frequency of operation.
PS / LD PU stop	Cause: The PU stop (stop of the converter operation by pressing STOP/RESET on the PU) is enabled by the setting of Pr.75. Remedy: To reset the indication, turn ON the Converter stop (SOF) signal to stop the converter output, and press EXT.
MT / LE Maintenance signal output	Cause: Appears when the converter's cumulative energization time reaches or exceeds the parameter set value (Pr.34 > Pr.35). Remedy: Write "0" in Pr.34 Maintenance timer.
CP Parameter copy	Cause: Appears when parameter copy is performed between the FR-XC-(H)55K or lower and the FR-XC-H75K. Remedy: Pr.52 PU main monitor selection and Pr.57 Restart selection must be set again. Set the initial value in Pr.989 Parameter copy alarm release.
SL / LG Power supply not detected	Cause: Appears when the power supply detection ends incompletely at a power failure. Appears at the power ON of the control circuit when using separate power supply sources for the control circuit and main circuit. Remedy: Check that the wiring from proper power source is performed correctly. Correct the wiring.
LH Converter operation disabled	Cause: Appears when the regenerative operation is not possible due to data processing in the converter (e.g. triggered by SOF signal). Remedy: Turn OFF the SOF signal. Check the power supply condition is stable. Check that the multifunction regeneration converter was reset after Parameter copy.
LJ Box-type reactor overheat pre-alarm	Cause: Appears when the speed of cooling fan on the box-type reactor decreases. Remedy: The fan may be faulty. Contact your sales representative. Check the cooling fan for a failure.
FN / LA Fan alarm	Cause: Appears when the cooling fan in the converter stops due to a fault or slows down. Remedy: The fan may be faulty. Contact your sales representative. Check the cooling fan for a failure.
E.OCT / E.A Overcurrent trip	Cause: The converter output is shut off if the input current exceeds the specified level during operation. Remedy: Check for sudden load change. Check for a short-circuit in the output circuit. Check that the wiring is performed correctly. Check that any power supply failure did not occur. Keep the load stable.
E.OVT / E.B Overvoltage trip	Cause: If the converter's internal main circuit DC voltage reaches or exceeds the specified value, the protective circuit is activated. Can also be caused by surge voltage. Remedy: Check for sudden load change and excessive regeneration. Check that any power supply failure did not occur. Keep the load stable. Check the power supply.
E.THT / E.C Overload trip (electronic thermal relay function)	Cause: Electronic thermal relay activates in inverse-time characteristics against the converter input to stop the output. Remedy: Reduce the load. Reconsider the configuration of the inverters for the converter. Make the permissible voltage imbalance ratio within 3%. Check that the total capacity of inverters is not larger than the converter capacity.
E.FIN / E.D Heat sink overheat	Cause: When the heat sink overheats, the temperature sensor activates, and the converter output is stopped. Remedy: Set the surrounding air temperature to within the specifications. Clean the heat sink (check for clogging). Replace the cooling fan if stopped.
E.IPF / E.E Instantaneous power failure	Cause: Instantaneous power failure protection function activates to stop the output. (Power failure persists for 100 ms or longer). Remedy: Remedy the instantaneous power failure. Prepare a backup power supply for instantaneous power failure. Set the function of automatic restart after instantaneous power failure (Pr.57).
E.UVT / E.F Undervoltage	Cause: If the power supply voltage drops to about 150 VAC or lower, the output is stopped to prevent control circuit malfunction. Remedy: Investigate the devices on the power system such as the power supply itself. Check if a high-capacity motor is driven. Check that the wiring is performed correctly.
E.ILF / E.G Input phase loss	Cause: This protective function is activated when any of the three phases of power input is lost. Remedy: Correct the wiring. Repair a broken wire.
E.OHT / E.H External thermal relay operation	Cause: If an overheat protection device such as a thermostat activates, the output of the converter is stopped. (Available when "4" is set in Pr.3, Pr.4, or Pr.7). Remedy: Check for the overheat of a thermostat or other similar peripheral devices. Check for a short circuit between terminals PC and SD. Check the wiring. Reset the thermostat (converter does not restart unless reset).
E.J / PUE / E.PUE PU disconnection	Cause: Communication between the converter and the PU is suspended (e.g., disconnected parameter unit) while Pr.75 is set to "2, 3, 16 or 17". Remedy: Check that the PU is connected properly. Check that the Pr.75 setting is correct. Set Pr.75 appropriately. Fit the PU securely.
E.K / RET / E.RET Retry count excess	Cause: Operation cannot be resumed properly within the set number of retries (enabled when Pr.67 is set). Remedy: Find the cause of the fault occurrence. Eliminate the cause of the error preceding this error indication.
E.L / CPU / E.CPU CPU fault	Cause: A communication fault in the built-in CPU has occurred. Remedy: Check for devices producing excess electrical noises around the converter. Take measures against noises. Contact your sales representative.
E.L / E13 / E.13 Internal circuit fault	Cause: An internal circuit fault has occurred. Remedy: Contact your sales representative.
E.M / P24 / E.P24 24 VDC power output short circuit	Cause: The 24 VDC power output from terminal PC is shorted. Remedy: Check for a short circuit in terminal PC. Repair the short-circuited portion. Reset via PU or power cycle (cannot be reset by external RES signal).
E.N / IOH / E.IOH Inrush overheat	Cause: Inrush current limit contactor does not turn ON, thermostat activates, or the circuit is damaged due to frequent power ON/OFF. Remedy: Check that frequent power ON/OFF is not repeated. Configure a circuit where frequent power ON/OFF is not repeated. If situation persists, contact your sales representative.
E.P / PE / E.PE Corrupt Memory (Control circuit board)	Cause: Parameter storage device fault (EEPROM failure) or too many parameter write times. Remedy: Set "1" in Pr.342 (write to RAM) for operations requiring frequent parameter writing. If situation persists, contact your sales representative.
E.P / PE2 / E.PE2 PR storage alarm (Main circuit board)	Cause: Parameter storage device fault (EEPROM failure) on the main circuit board. Remedy: Contact your sales representative.
E.Q / OP1 / E.OP1 Communication option fault	Cause: Communication line error, wrong option setting, loose connector, cable break, or terminating resistor issue. Remedy: Check the option function setting. Connect the communication option securely. Check the connection of communication cables.
E.T / ERR / E.MF1 Connection mode fault	Cause: Connection mode selection switch does not match the actual wiring of main circuit terminals. Remedy: Check that the setting of Pr.415 SW2 setting status is correct. Check the wiring. Set Pr.415 appropriately.
E.U / ERR / E.MF2 Unsupported control selection	Cause: Unsupported function is set to be enabled by using Pr.416. Remedy: Check the setting of Pr.416. Set Pr.416 correctly.
E.V / ERR / E.FT1 Box-type reactor overheat protection	Cause: Reactor overheat (LOH) signal detected, Pr.416 setting mismatch, installation error, or cooling fan failure. Remedy: Remove foreign matter from cooling fan. Set Pr.416 correctly (match reactor model). Check the wiring. Contact sales representative if needed.
E.W / ERR / E.FT2 Box-type reactor cooling fan power short	Cause: Power supply for the cooling fan on the box-type reactor is shorted. Remedy: Check for a short circuit in power supply for the cooling fan. Correct the wiring.
E.1 / E.1 Option fault	Cause: Contact failure between converter and option, switch setting changed, or excess electrical noise. Remedy: Connect the communication option securely. Take measures against noises. Set the switch for manufacturer setting back to initial position. Contact sales representative if unresolved.
E.6 / E.16 Main circuit power supply detection fault	Cause: Power supply to the main circuit is not detected. Remedy: Contact your sales representative.
E.8 / E.8 Input power supply fault 1	Cause: Power supply frequency fault, phase detection failure, overvoltage, sudden amplitude change, or wiring error (R, S, T). Remedy: Check that the wiring from proper power source is performed correctly. Correct the wiring.

 

How to Read FR-XC Faults via FR Configurator2

Since the FR-XC often operates in the background of a larger drive system, getting accurate diagnostics in 2026 requires connecting to the unit (or the main inverter) using Mitsubishi’s FR Configurator2 software. Here is how to utilize the software for troubleshooting:

• Converter Status Monitoring: Unlike standard drives that monitor motor speed, the FR-XC diagnostic tools focus on AC Input Voltage and DC Bus Voltage. Use the software to check if the grid voltage dropped or spiked immediately before the fault.
• Alarm History: The unit stores the last 8 alarm records (typically E.A through E.Z codes). This history helps identify if specific faults correspond with grid switching events or heavy braking cycles.
• Life Diagnosis: The FR-XC contains critical components like cooling fans and smoothing capacitors. The software provides a “Life Diagnosis” readout to warn you if component deterioration is causing nuisance tripping (e.g., overheating due to a slow fan).

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Frequently Asked Questions (FAQ)

Q: What is the function of the FR-XC compared to a standard VFD?
A: The FR-XC is not a motor driver; it is a power converter. It allows braking energy from the motor to flow back into the power grid (Regeneration) rather than burning it off as heat in a resistor. Faults here usually relate to grid power quality (Phase Loss) or DC voltage regulation.

Q: How do I reset a Mitsubishi FR-XC fault?
A: You can reset the converter by switching the power off and on, or by turning on the RES (Reset) signal connected to the control terminal block. If the FR-XC is connected to an inverter via the “Inverter-to-converter link,” resetting the main inverter may also reset the converter.

Q: What does fault “E.A” usually indicate on an FR-XC?
A: “E.A” typically indicates an internal hardware error or an Instantaneous Power Failure. Check the wiring of the phase detection terminals (R/S/T) and ensure the mode selection switches (functions 1, 2, or 3) are set correctly for your specific wiring configuration.