Mitsubishi FR Inverter Alarm Codes

E.OC1: Overcurrent trip during acceleration

What it means: Output current reached about 200% of the inverter rated current (FR-D700) or about 230% (FR-E700) while the motor was accelerating, so the inverter shut off its output.^{[1][2][3][4][5]}

Also on: FR-A700 (about 220%), FR-A800 (about 235%), FR-E800 (about 230% at ND rating): same code and name

Likely causes

• Acceleration time too short for the load or inertia
• Short circuit or ground fault in the motor or output cable
• Pr.3 Base frequency set to 60 Hz on a 50 Hz motor
• Stall prevention level set too high, or fast-response current limit disabled
• Frequent regeneration pushing the output voltage above the V/F pattern
• Downward acceleration time too long on a lift or hoist

First checks, in this order

1. Increase Pr.7 Acceleration time (on a lift, shorten the downward acceleration time).
2. Check the output wiring and motor for a short circuit or ground fault.
3. Set Pr.3 Base frequency to the motor rated frequency and Pr.19 Base frequency voltage to the motor rated voltage.
4. Lower the stall prevention level (Pr.22) and enable fast-response current limit in Pr.156.
5. If E.OC1 appears at every start, disconnect the motor and start again. If it still appears, contact Mitsubishi service.

E.OV3: Regenerative overvoltage trip during deceleration or stop

What it means: Energy fed back by the motor while slowing down pushed the main circuit DC voltage over the trip level, so the inverter shut off. A surge on the supply can also cause it.^{[1][2][3][4][5]}

Also on: FR-A700, FR-A800, FR-E800 (same code and name)

Likely causes

• Deceleration time too short for the load inertia
• Braking cycle too frequent
• Brake resistor or brake unit missing, undersized or faulty
• Surge voltage on the supply

First checks, in this order

1. Increase Pr.8 Deceleration time to match the load inertia.
2. Make the braking cycle longer.
3. Use the regeneration avoidance function (Pr.882, Pr.883, Pr.885, Pr.886).
4. Fit or check a brake resistor, brake unit or power regeneration common converter (FR-CV) as needed.
5. Set Pr.154 Voltage reduction selection during stall prevention operation to 11 (where available).

E.THM: Motor overload trip (electronic thermal O/L relay function)

What it means: The electronic thermal model in the inverter calculates that the motor has overheated from overload or poor cooling at low speed. TH appears at 85% of the Pr.9 setting and the trip comes at 100%.^{[1][2][3][4][5]}

Also on: FR-A700 (named Motor overload trip (electronic thermal relay function)), FR-A800, FR-E800

Likely causes

• Motor overloaded
• Long running at low speed with a self-cooled motor
• Pr.9 Electronic thermal O/L relay not set to the motor rated current
• Pr.71 Applied motor set wrong (for example a constant-torque motor set as a standard motor)
• Stall prevention settings wrong

First checks, in this order

1. Reduce the load and check the machine for binding.
2. Set Pr.9 to the motor rated current.
3. Check Pr.71 Applied motor and select the constant-torque motor setting when one is used.
4. Check the stall prevention settings (Pr.22, Pr.156).
5. For multi-pole motors or several motors on one inverter, fit an external thermal relay on the output side, because the electronic thermal cannot protect them.
6. A reset clears the thermal memory, so let the motor cool before restarting.

E.OC2: Overcurrent trip during constant speed

What it means: Output current reached about 200% (FR-D700) or about 230% (FR-E700) of the rated current while running at constant speed.^{[1][2][3][4][5]}

Also on: FR-A700, FR-A800, FR-E800 (same code and name)

Likely causes

• Sudden load change or a jam
• Short circuit or ground fault on the output side
• Stall prevention level set too high, or fast-response current limit disabled

First checks, in this order

1. Check the machine for sudden load changes and keep the load steady.
2. Check the output wiring and the motor insulation.
3. Lower Pr.22 and enable fast-response current limit in Pr.156.

E.OC3: Overcurrent trip during deceleration or stop

What it means: Output current reached about 200% (FR-D700) or about 230% (FR-E700) of the rated current while decelerating or at stop.^{[1][2][3][4][5]}

Also on: FR-A700, FR-A800, FR-E800 (same code and name)

Likely causes

• Deceleration too fast
• Short circuit or ground fault on the output side
• Motor mechanical brake closing too early
• Stall prevention level set too high, or fast-response current limit disabled

First checks, in this order

1. Increase Pr.8 Deceleration time.
2. Check the output wiring and the motor insulation.
3. Check the mechanical brake timing.
4. Lower Pr.22 and enable fast-response current limit in Pr.156.

E.OV1: Regenerative overvoltage trip during acceleration

What it means: The main circuit DC voltage went over the trip level while accelerating, usually from regenerative energy (for example a load lowering on a lift) or a supply surge.^{[1][2][3][4][5]}

Also on: FR-A700, FR-A800, FR-E800 (same code and name)

Likely causes

• Acceleration too slow while the load drives the motor (downward travel on a vertical lift)
• Pr.22 Stall prevention operation level set too low
• Stall prevention acting often on a high-inertia load
• Surge voltage on the supply

First checks, in this order

1. Shorten Pr.7 Acceleration time where the load drives the motor.
2. Set Pr.22 correctly (above the motor no-load current).
3. Use the regeneration avoidance function (Pr.882, Pr.883, Pr.885, Pr.886).
4. Set Pr.154 to 11 (where available).

E.OV2: Regenerative overvoltage trip during constant speed

What it means: The main circuit DC voltage went over the trip level at constant speed, usually because the load is driving the motor or changed suddenly.^{[1][2][3][4][5]}

Also on: FR-A700, FR-A800, FR-E800 (same code and name)

Likely causes

• Sudden load change or an overhauling load
• Pr.22 Stall prevention operation level set too low
• Stall prevention acting often on a high-inertia load
• Surge voltage on the supply

First checks, in this order

1. Keep the load steady.
2. Use the regeneration avoidance function (Pr.882, Pr.883, Pr.885, Pr.886).
3. Add a brake resistor, brake unit or FR-CV as needed.
4. Set Pr.22 correctly and set Pr.154 to 11 (where available).

E.THT: Inverter overload trip (electronic thermal O/L relay function)

What it means: Current at or above the inverter rating for too long heated the output transistors past their protection level. Overload capacity is 150% for 60 s, and 200% for 0.5 s (FR-D700) or 3 s (FR-E700).^{[1][2][3][4][5]}

Also on: FR-A700, FR-A800, FR-E800 (same code, name worded slightly differently)

Likely causes

• Acceleration or deceleration time too short
• Torque boost set too high or too low
• Pr.14 Load pattern selection wrong for the machine
• Motor overloaded
• Surrounding air temperature too high

First checks, in this order

1. Increase Pr.7 and Pr.8.
2. Adjust Pr.0 Torque boost.
3. Set Pr.14 Load pattern selection to match the machine.
4. Reduce the load or check that the inverter is sized for the motor and duty.
5. Bring the surrounding air temperature within specification.

OL: Stall prevention (overcurrent)

What it means: Output current went above the stall prevention level (Pr.22, 150% by default), so the inverter holds or lowers the frequency to avoid an overcurrent trip. The drive keeps running, but speed changes take longer.^{[1][2][3][4][5]}

Also on: FR-A700, FR-A800 (same code and name); FR-E800 shows OLC on its operation panel

Likely causes

• Pr.7 Acceleration time or Pr.8 Deceleration time too short
• Pr.0 Torque boost too high
• Load too heavy, or a fault in peripheral equipment
• Pr.13 Starting frequency too high
• Pr.22 Stall prevention operation level not suited to the load

First checks, in this order

1. Increase Pr.7 and Pr.8.
2. Change Pr.0 Torque boost 1% at a time while watching the motor.
3. Reduce the load.
4. Try magnetic flux vector control or change Pr.14 Load pattern selection.
5. Raise Pr.22, or disable stall prevention with Pr.156.

oL: Stall prevention (overvoltage)

What it means: Regenerative energy during deceleration is more than the inverter can absorb, so it pauses deceleration (or, with Pr.882 = 1, raises speed) to avoid an overvoltage trip. The drive keeps running and the stop takes longer.^{[1][2][3][4][5]}

Also on: FR-A700, FR-A800 (same code and name); FR-E800 shows OLV on its operation panel

Likely causes

• Sudden speed reduction
• High-inertia load
• Regeneration avoidance function active (Pr.882)

First checks, in this order

1. Increase Pr.8 Deceleration time.
2. Check the regeneration avoidance settings (Pr.882, Pr.883, Pr.885, Pr.886).

E.FIN: Heatsink overheat

What it means: The heatsink temperature sensor tripped the inverter. The FIN output signal can warn at about 85% of the trip temperature.^{[1][2][3][4][5]}

Also on: FR-A700 (same name); FR-A800 and FR-E800 (named Heat sink overheat)

Likely causes

• Surrounding air temperature too high
• Heatsink fins clogged with dust
• Cooling fan stopped (FN shown on the panel)

First checks, in this order

1. Bring the surrounding air temperature within specification and check cabinet ventilation.
2. Clean the heatsink.
3. Check the cooling fan and replace it if it has stopped.
4. For an early warning, assign FIN (26 or 126) to an output terminal with Pr.190, Pr.192 or Pr.197 (FR-D700) or Pr.190 to Pr.192 (FR-E700).

E.GF: Output side earth (ground) fault overcurrent at start

What it means: At start, the inverter detected earth fault current on its output (motor) side and shut off. This check only runs when Pr.249 Earth (ground) fault detection at start is enabled; the initial setting 0 turns it off.^[1][2]

Likely causes

• Ground fault in the motor windings
• Damaged motor cable insulation to earth

First checks, in this order

1. Disconnect the motor cable from the inverter and check the motor and cable insulation to earth.
2. Repair the faulty part.
3. Check the Pr.249 setting.

E.LF: Output phase loss

What it means: One of the output phases U, V or W was lost while running (not checked during DC injection braking or below 1 Hz). It works when Pr.251 Output phase loss protection selection is enabled.^{[1][2][3][4][5]}

Also on: FR-A700, FR-A800, FR-E800 (same code and name)

Likely causes

• Broken or loose motor cable or terminal
• Open motor winding
• Motor much smaller than the inverter

First checks, in this order

1. Check the wiring and terminals between inverter and motor.
2. Check the motor windings.
3. Check that the motor capacity is not smaller than the inverter capacity.
4. Check the Pr.251 setting.

E.ILF: Input phase loss

What it means: One phase of the three-phase supply was lost, or the phase-to-phase voltages are badly unbalanced. Active only when Pr.872 Input phase loss protection selection = 1 (the initial 0 turns it off), and only on three-phase input models.^{[1][2][3][4][5]}

Also on: FR-A700, FR-A800, FR-E800 (same code and name)

Likely causes

• Blown fuse or open breaker pole
• Broken supply cable
• Large supply voltage unbalance

First checks, in this order

1. Measure all three supply phases at the input terminals.
2. Repair the broken cable or fuse.
3. If the supply is permanently unbalanced, set Pr.872 = 0.

UV: Undervoltage

What it means: The supply voltage fell below about 115 V AC (about 230 V AC on the 400 V class, about 58 V AC on the 100 V class), so the inverter stops its output and shows UV. It clears by itself when the voltage returns to normal.^[1][2][5]

Also on: FR-E800 (same code and name)

Likely causes

• Supply voltage dip or weak supply
• Fault in the supply equipment, such as a breaker or contactor

First checks, in this order

1. Measure the supply voltage at the input terminals.
2. Check the power supply equipment, breaker and contactor.

FN: Fan alarm

What it means: The cooling fan stopped because of a fault, or runs differently from the Pr.244 Cooling fan operation selection setting. The inverter keeps running, but E.FIN can follow.^{[1][2][3][4][5]}

Also on: FR-A700, FR-A800, FR-E800 (same code and name; on the FR-E800 also check that a replaced fan was not fitted upside down)

Likely causes

• Cooling fan failed or blocked
• Pr.244 setting different from the expected fan operation

First checks, in this order

1. Check that the fan turns freely and is free of dust and debris.
2. Check Pr.244.
3. Replace the fan or contact Mitsubishi service if it is faulty.

E.BE: Brake transistor alarm detection

What it means: The built-in brake transistor circuit has failed, for example from very large regenerative energy. Mitsubishi says to switch the inverter power off immediately.^{[1][2][3][4][5]}

Also on: FR-A700, FR-A800, FR-E800 (same code and name)

Likely causes

• Excessive regenerative energy from the load
• Brake used too often
• Wrong brake resistor selected

First checks, in this order

1. Switch off the inverter power at once.
2. Reduce the load inertia or the braking duty.
3. Check the brake resistor selection and how often it is used.
4. Replace the inverter.

E.OLT: Stall prevention stop

What it means: Stall prevention pulled the output frequency down to 1 Hz and it stayed there for 3 s, so the inverter tripped. OL is shown while stall prevention is acting.^{[1][2][3][4][5]}

Also on: FR-A700 (0.5 Hz under V/F control), FR-A800, FR-E800 (same code and name)

Likely causes

• Motor overloaded or the machine jammed
• Pr.22 Stall prevention operation level set too low

First checks, in this order

1. Reduce the load and check the machine for jams.
2. Check Pr.22.

E.OHT: External thermal relay operation

What it means: An external motor thermal relay or a thermostat in the motor opened its contact on an input set to OH (value 7), so the inverter stopped.^{[1][2][3][4][5]}

Also on: FR-A700 (inputs Pr.178 to Pr.189), FR-A800, FR-E800 (same code and name)

Likely causes

• Motor overheated
• Input terminal wrongly set to 7 (OH signal)
• Thermal relay circuit open

First checks, in this order

1. Check the motor temperature, load and cooling.
2. Check which input in Pr.178 to Pr.182 (FR-D700) or Pr.178 to Pr.184 (FR-E700) is set to 7.
3. Reduce the load and the operating duty.
4. Reset the inverter after the relay recovers; it does not restart by itself.

TH: Electronic thermal relay function pre-alarm

What it means: The motor electronic thermal value has reached 85% of the Pr.9 setting. At 100% the inverter trips with E.THM.^{[1][2][3][4][5]}

Also on: FR-A700, FR-A800, FR-E800 (same code and name)

Likely causes

• Heavy load or sudden acceleration
• Pr.9 Electronic thermal O/L relay set wrong

First checks, in this order

1. Reduce the load and how often the machine runs.
2. Set Pr.9 to the motor rated current.
3. To signal it, assign THP (8 or 108) to an output terminal.

RB: Regenerative brake pre-alarm

What it means: The regenerative brake duty has reached 85% of the Pr.70 Special regenerative brake duty value. At 100% a regenerative overvoltage trip (E.OV1 to E.OV3) follows.^{[1][2][3][4][5]}

Also on: FR-A700, FR-A800, FR-E800 (same code and name)

Likely causes

• Brake resistor duty too high
• Pr.30 Regenerative function selection or Pr.70 set wrong
• Deceleration too fast

First checks, in this order

1. Increase the deceleration time.
2. Check Pr.30 and Pr.70.
3. To signal it, assign RBP (7 or 107) to an output terminal.

PS: PU stop

What it means: The STOP/RESET key on the operation panel was pressed while the inverter was running from external or network commands (allowed by Pr.75), so the motor stopped.^{[1][2][3][4][5]}

Also on: FR-A700, FR-A800, FR-E800 (same code and name)

Likely causes

• STOP/RESET key pressed during External or NET operation

First checks, in this order

1. Turn the start signal off, then release the stop from the operation panel (the PU/EXT key on the FR-E800).
2. Check Pr.75 Reset selection/disconnected PU detection/PU stop selection.

E.PE: Parameter storage device fault (control circuit board)

What it means: The EEPROM that stores the parameters on the control board has a fault.^{[1][2][3][4][5]}

Also on: FR-A700, FR-A800, FR-E800 (same code and name)

Likely causes

• Too many parameter writes, for example frequent writes over communication
• Control board memory failure

First checks, in this order

1. If a PLC writes parameters often, set Pr.342 = 1 to write to RAM only (RAM values are lost at power off).
2. Contact Mitsubishi service.

E.CPU: CPU fault

What it means: Communication with the built-in CPU failed, so the inverter stopped. The same fault can show as E.5 (and on the FR-E700 also E.6 or E.7).^{[1][2][3][4][5]}

Also on: FR-A700, FR-A800, FR-E800 (same code and name)

Likely causes

• Electrical noise from nearby equipment
• Internal fault

First checks, in this order

1. Look for noisy equipment near the inverter and take noise countermeasures.
2. Contact Mitsubishi service if it repeats.

E.5: CPU fault

What it means: Another display of the CPU fault: communication with the built-in CPU failed. The panel shows it with a blank after the dot (E. 5).^{[1][2][3][4][5]}

Also on: FR-A700, FR-A800, FR-E800 (same code and name)

Likely causes

• Electrical noise from nearby equipment
• Internal fault

First checks, in this order

1. Take noise countermeasures around the inverter.
2. Contact Mitsubishi service if it repeats.

E.6: CPU fault

What it means: CPU fault display used on the FR-E700. Besides noise, Mitsubishi points to a short between control terminals PC and SD.^[2][3][4][5]

Also on: FR-A700, FR-A800, FR-E800 (same code and name)

Likely causes

• Terminals PC and SD shorted
• Electrical noise from nearby equipment
• Internal fault

First checks, in this order

1. Check the wiring between terminals PC and SD and remove any short.
2. Take noise countermeasures around the inverter.
3. Contact Mitsubishi service if it repeats.

E.7: CPU fault

What it means: CPU fault display used on the FR-E700. Besides noise, Mitsubishi points to a short between control terminals PC and SD.^[2][3][4][5]

Also on: FR-A700, FR-A800, FR-E800 (same code and name)

Likely causes

• Terminals PC and SD shorted
• Electrical noise from nearby equipment
• Internal fault

First checks, in this order

1. Check the wiring between terminals PC and SD and remove any short.
2. Take noise countermeasures around the inverter.
3. Contact Mitsubishi service if it repeats.

E.PUE: PU disconnection

What it means: Communication with the operation panel or parameter unit on the PU connector was lost while Pr.75 is set to detect it (2, 3, 16 or 17), or RS-485 errors on the PU connector went past the Pr.121 retry count or the Pr.122 check time.^{[1][2][3][4][5]}

Also on: FR-A700, FR-A800, FR-E800 (same code and name)

Likely causes

• Parameter unit cable loose or unplugged
• Pr.75 set to detect PU disconnection
• RS-485 settings on the inverter different from the computer
• Host not sending data within the Pr.122 time

First checks, in this order

1. Reconnect the parameter unit cable securely.
2. Check Pr.75.
3. For RS-485 on the PU connector, check that the communication settings match the computer and that data arrives within Pr.122 (or set Pr.122 = 9999 to turn the check off).

E.RET: Retry count excess

What it means: The automatic retry function (Pr.67 Number of retries at fault occurrence) could not restart the inverter within the set number of retries.^{[1][2][3][4][5]}

Also on: FR-A700, FR-A800, FR-E800 (same code and name)

Likely causes

• A repeating fault that the retries could not clear

First checks, in this order

1. Find and fix the fault that started the retries (check the faults history).

HOLD: Operation panel lock

What it means: The operation panel is locked, so only the STOP/RESET key works. This is a message, not a fault.^{[1][2][3][4][5]}

Also on: FR-A700, FR-A800, FR-E800 (same code and name)

Likely causes

• Operation lock mode set on the panel

First checks, in this order

1. Press MODE for 2 s to release the lock.

LOCD: Password locked

What it means: Password protection is active, so parameter display and setting are restricted.^{[1][2][3][4][5]}

Also on: FR-A700, FR-A800, FR-E800 (same code and name)

Likely causes

• Password lock set in Pr.296 and Pr.297

First checks, in this order

1. Enter the password in Pr.297 Password lock/unlock.

Er1: Write disable error

What it means: A parameter write was refused because Pr.77 blocks writing, frequency jump ranges overlap, or the PU and inverter cannot communicate normally.^{[1][2][3][4][5]}

Also on: FR-A700, FR-A800, FR-E800 (same code and name)

Likely causes

• Pr.77 Parameter write selection set to disable writes
• Overlapping frequency jump ranges in Pr.31 to Pr.36
• PU communication problem

First checks, in this order

1. Check Pr.77.
2. Check Pr.31 to Pr.36.
3. Check the PU connection.

Er2: Write error during operation

What it means: A parameter was written while the inverter was running (STF or STR on) and Pr.77 is not set to 2.^{[1][2][3][4][5]}

Also on: FR-A700, FR-A800, FR-E800 (same code and name)

Likely causes

• Parameter change attempted during operation

First checks, in this order

1. Stop the inverter before changing parameters.
2. Or set Pr.77 = 2 to allow writing during operation.

Er3: Calibration error

What it means: The analog input bias and gain calibration points are set too close together.^{[1][2][3][4][5]}

Also on: FR-A700, FR-A800, FR-E800 (same code and name)

Likely causes

• Bias and gain calibration values too close

First checks, in this order

1. Check calibration parameters C3, C4, C6 and C7.

Er4: Mode designation error

What it means: A parameter was set in External or NET operation mode while Pr.77 is not 2, or the command source is not the operation panel.^{[1][2][3][4][5]}

Also on: FR-A700, FR-A800, FR-E800 (same code and name)

Likely causes

• Inverter not in PU operation mode
• Pr.77 not set to 2
• Parameter unit or FR Configurator connected while Pr.551 = 9999 (initial)

First checks, in this order

1. Switch to PU operation mode, then set the parameter.
2. Or set Pr.77 = 2.
3. Disconnect the parameter unit, or check Pr.551 (set it to 4 to use the panel).

Err.: Inverter reset

What it means: The inverter is being reset by the RES signal or by a reset command from communication or the PU, or it is powering off. Err. blinks while the RES signal stays on.^[1][2][3][5]

Also on: FR-A700, FR-E800 (same code, named Error; on the FR-E800 it can also appear when the input voltage drops)

Likely causes

• RES signal held on
• Reset command from communication or the PU
• Power being switched off

First checks, in this order

1. Turn the reset command (RES signal) off.

MT: Maintenance signal output

What it means: The cumulative energization time of the inverter has reached the time set in Pr.504 Maintenance timer alarm output set time.^{[1][2][3][4][5]}

Also on: FR-A700, FR-A800 (same code and name); FR-E800 (named Maintenance timer)

Likely causes

• Maintenance interval set in Pr.504 reached

First checks, in this order

1. Carry out the planned maintenance.
2. Set Pr.503 Maintenance timer = 0 to clear the indication.
3. With Pr.504 = 9999 (initial) MT never appears.

SA: Safety stop

What it means: The safety stop function is active and the output is shut off through safety inputs S1 and S2. It is a status indication, not a trip (FR-E700: safety stop function models only).^[1][2][4][5]

Also on: FR-A800, FR-E800 (same code and name)

Likely causes

• Emergency stop or safety relay opened S1 or S2
• Shorting wires removed while the safety stop function is not used

First checks, in this order

1. If safety stop is not used, fit the shorting wires: S1 to SC and S2 to SC on the FR-D700, S1 to PC and S2 to PC on the FR-E700.
2. If it is used, find why the safety circuit opened and make the machine safe before restarting.
3. If SA shows with both inputs closed, check the S1 and S2 wiring and contact Mitsubishi service.

E.SAF: Safety circuit fault

What it means: The safety circuit is malfunctioning, or only one of the two safety lines (S1 or S2) is open (FR-E700: safety stop function models only).^[1][2][4][5]

Also on: FR-A800, FR-E800 (same code and name)

Likely causes

• One shorting wire missing while the safety stop function is not used
• Fault in the safety relay module or its wiring
• Internal safety circuit fault

First checks, in this order

1. When safety stop is not used, check the shorting wires: S1 to SC and S2 to SC (FR-D700), S1 to PC and S2 to PC (FR-E700).
2. When it is used, check the S1 and S2 wiring and that the safety relay module works.
3. See the Safety stop function instruction manual (BCN-A211508-000 for FR-D700, BCN-A211508-004 for FR-E700).

E.PTC: PTC thermistor operation

What it means: The motor PTC thermistor connected between terminals 2 and 10 measured more than the Pr.561 PTC thermistor protection level, so the inverter stopped. Off when Pr.561 = 9999 (initial).^[1][3][4][5]

Also on: FR-E800 (same terminals, plus Pr.1016 detection time); FR-A700 (thermistor on terminal AU with Pr.184 = 63); FR-A800 (same code and name)

Likely causes

• Motor overheated or overloaded
• Thermistor wiring open
• Pr.561 level set wrong

First checks, in this order

1. Check the motor load and cooling.
2. Check the thermistor connection to terminals 2 and 10.
3. Check Pr.561.

E.CDO: Output current detection value exceeded

What it means: Output current went above the Pr.150 Output current detection level and Pr.167 is set to stop the inverter when that happens.^[1][3][4][5]

Also on: FR-A700 (same code and name); FR-A800 and FR-E800 (same code, named Abnormal output current detection)

Likely causes

• Load current above the level set in Pr.150
• Detection level or timing set too tight

First checks, in this order

1. Check Pr.150, Pr.151, Pr.166 and Pr.167.
2. Check the machine for the cause of the high current.

E.IOH: Inrush current limit circuit fault

What it means: The resistor in the inrush current limit circuit overheated.^{[1][2][3][4][5]}

Also on: FR-A700 (also check the inrush contactor supply fuse on 110K and larger), FR-A800, FR-E800

Likely causes

• Power switched on and off too often
• Inrush current limit circuit fault

First checks, in this order

1. Change the control so the inverter power is not cycled frequently.
2. Contact Mitsubishi service if it persists.

E.AIE: Analog input fault

What it means: A signal on terminal 4 does not match Pr.267 Terminal 4 input selection and the voltage/current input switch.^{[1][2][3][4][5]}

Also on: FR-A700 (trips on 30 mA or 7.5 V or more at terminal 2 or 4 in current mode), FR-A800, FR-E800

Likely causes

• Pr.267 and the input switch set differently from the actual signal

First checks, in this order

1. Check Pr.267 and the voltage/current input switch.
2. Either feed a current signal, or set Pr.267 and the switch to voltage input.

E.OPT: Option fault

What it means: A communication option is fitted while Pr.296 Password lock level is 0 or 100.^[2][3][4][5]

Also on: FR-A700, FR-A800, FR-E800 (same code and name; there it also covers other option problems, such as a missing torque command option)

Likely causes

• Password lock level Pr.296 set to 0 or 100 with a communication option fitted

First checks, in this order

1. Check Pr.296. To use the password lock with a communication option, set Pr.296 to a value other than 0 or 100.
2. Contact Mitsubishi service if it persists.

E.OP1: Communication option fault

What it means: A communication line error occurred in the plug-in communication option.^[2][4][5]

Also on: FR-A800 (E.OP1 to E.OP3), FR-E800

Likely causes

• Wrong option function settings
• Plug-in option not seated in its connector
• Broken communication cable
• Terminating resistor missing or wrong

First checks, in this order

1. Check the option function settings.
2. Seat the plug-in option firmly.
3. Check the communication cable and the terminating resistor.

E.1: Option fault

What it means: Contact fault in the connector between the inverter and the plug-in option, or the option's manufacturer setting switch was changed.^[2][3][4][5]

Also on: FR-A700 and FR-A800 (E.1 to E.3, the number is the option connector), FR-E800

Likely causes

• Plug-in option loose in its connector
• Electrical noise
• Manufacturer setting switch on the option changed

First checks, in this order

1. Reseat the plug-in option.
2. Take noise countermeasures around the inverter.
3. Return the option's manufacturer setting switch to its initial position.
4. Contact Mitsubishi service if it persists.

E.PE2: Internal board fault

What it means: On the FR-E700 this means the control board and main circuit board do not form a valid combination, so the inverter tripped.^[2]

Likely causes

• Wrong combination of control board and main circuit board, for example after a board swap

First checks, in this order

1. Contact Mitsubishi service; board replacement goes through a Mitsubishi Electric FA Center.

E.MB4 to E.MB7: Brake sequence fault

What it means: A sequence error occurred while the brake sequence function (Pr.278 to Pr.283) was in use. Off in the initial setting.^[2][3][4][5]

Also on: FR-A700 (E.MB1 to E.MB7, Pr.278 to Pr.285), FR-A800 and FR-E800 (E.MB1 to E.MB7)

Likely causes

• Brake sequence parameters set wrong
• Wiring fault in the brake sequence signals

First checks, in this order

1. Find the cause of the sequence error.
2. Check the brake sequence parameters and the wiring.

E.USB: USB communication fault

What it means: USB communication stopped for longer than Pr.548 USB communication check time interval.^[2][3][4][5]

Also on: FR-A700, FR-A800, FR-E800 (same code and name)

Likely causes

• USB cable unplugged or faulty
• Pr.548 set too short

First checks, in this order

1. Check the USB cable.
2. Increase Pr.548, or set it to 9999 to turn the check off.

E.13: Internal circuit fault

What it means: An internal circuit fault occurred and the inverter stopped its output.^[2][3][4][5]

Also on: FR-A700, FR-A800, FR-E800 (same code and name)

Likely causes

• Internal hardware fault

First checks, in this order

1. Contact Mitsubishi service.

EV: 24V external power supply operation

What it means: Blinks while the control circuit runs on 24 V external power (FR-E7DS fitted) and the main circuit power is off.^[2][4][5]

Also on: FR-A800, FR-E800 (same code)

Likely causes

• Main circuit power off or low
• Jumper between terminals P/+ and P1 removed

First checks, in this order

1. Switch on the main circuit power and check its voltage.
2. Check that the jumper between P/+ and P1 is fitted securely.

E.GF: Output side earth (ground) fault overcurrent

What it means: On these models the inverter checks for earth fault current on its output (motor) side during operation, not only at start, and shuts off when it finds one.^[3][4][5]

Also on: FR-A800, FR-E800 (same code and name)

Likely causes

• Ground fault in the motor windings
• Damaged motor cable insulation to earth

First checks, in this order

1. Disconnect the motor cable from the inverter and check the motor and cable insulation to earth.
2. Repair the earth fault.

E.UVT: Undervoltage

What it means: The supply voltage fell below about 150 V AC (300 V AC on the 400 V class) and the inverter tripped. It also trips if the jumper between P/+ and P1 is missing.^[3][4][5]

Also on: FR-A800 (same code and name); FR-E800 (same code and name, described for PM motor restart after a supply drop)

Likely causes

• Supply dip, for example when a large motor starts on the same supply
• Jumper or DC reactor between P/+ and P1 missing
• Fault in the supply equipment

First checks, in this order

1. Check for large motors starting on the same supply.
2. Fit the jumper or a DC reactor across P/+ and P1.
3. Check the power supply equipment.

E.IPF: Instantaneous power failure

What it means: Power was lost for more than 15 ms, so the inverter tripped to protect its control circuit. If the loss lasts more than 100 ms, the fault output is not given and the inverter restarts when power returns if the start signal is on.^[3][4]

Also on: FR-A800 (same code and name; 10 ms on IP55 models)

Likely causes

• Short supply interruption or dip
• Input power switched off while running

First checks, in this order

1. Find the cause of the power loss.
2. Add a backup supply if needed.
3. Use automatic restart after instantaneous power failure (Pr.57).

E.PE2: Parameter storage device fault (main circuit board)

What it means: On these models E.PE2 means the parameter memory on the main circuit board has a fault.^[3][4][5]

Also on: FR-A800, FR-E800 (same code and name)

Likely causes

• Main circuit board memory fault

First checks, in this order

1. Contact Mitsubishi service.

E.CTE: Operation panel power supply short circuit, RS-485 terminal power supply short circuit

What it means: The power supply for the PU connector or for the RS-485 terminals is shorted, so that supply is cut and the inverter stops.^[3][4]

Also on: FR-A800 (same code and name)

Likely causes

• Short in the PU cable or parameter unit
• Wrong wiring on the RS-485 terminals

First checks, in this order

1. Check the PU cable and parameter unit.
2. Check the RS-485 terminal wiring.
3. Reset with the RES signal or by switching the power off and on.

E.P24: 24VDC power output short circuit

What it means: The 24 V DC output at terminal PC is shorted, so it is cut off and all external contact inputs switch off.^[3][4]

Also on: FR-A800 (same code, named 24 VDC power fault)

Likely causes

• Short circuit or earth fault on wiring from terminal PC

First checks, in this order

1. Find and remove the short on the PC terminal wiring.
2. Reset from the operation panel or by switching the power off and on; the RES signal cannot reset this fault.

E.SER: Communication fault (inverter)

What it means: RS-485 communication through the RS-485 terminals failed more times than Pr.335 allows, or stopped for longer than Pr.336.^[3][4]

Also on: FR-A800 (same code and name)

Likely causes

• RS-485 terminal wiring fault
• Host stopped sending

First checks, in this order

1. Check the RS-485 terminal wiring.
2. Check Pr.335 RS-485 communication retry count and Pr.336 RS-485 communication check time interval.

E.OS: Overspeed occurrence

What it means: Motor speed went above Pr.374 Overspeed detection level under encoder feedback, Real sensorless vector or vector control. Off in the initial setting on the FR-A700.^[3][4][5]

Also on: FR-A800, FR-E800 (same code and name; with Pr.374 = 9999 they trip at maximum frequency + 20 Hz)

Likely causes

• Pr.374 set too low
• Pr.369 Number of encoder pulses different from the actual encoder

First checks, in this order

1. Check Pr.374.
2. Check that Pr.369 matches the encoder.

E.OSD: Speed deviation excess detection

What it means: Under vector control with Pr.285 set, the load pushed motor speed away from the command and the inverter could not correct it.^[3][4][5]

Also on: FR-A800, FR-E800 (same code and name)

Likely causes

• Sudden load change
• Pr.285 or Pr.853 set wrong
• Pr.369 Number of encoder pulses wrong

First checks, in this order

1. Check Pr.285 and Pr.853 Speed deviation time.
2. Keep the load steady.
3. Check Pr.369.

E.ECT: Signal loss detection

What it means: The encoder signal was lost under orientation control, encoder feedback control or vector control.^[3][4][5]

Also on: FR-A800, FR-E800 (same code and name)

Likely causes

• Encoder cable broken or connector loose
• Wrong encoder specification or option switch setting (FR-A7AP or FR-A7AL)
• Encoder powered later than the inverter, or wrong encoder supply voltage

First checks, in this order

1. Check the encoder cable and connectors.
2. Check the encoder specification and the switch setting on the FR-A7AP or FR-A7AL.
3. Power the encoder together with the inverter; if it must come later, set Pr.376 = 0.
4. Match the encoder supply voltage to the encoder output voltage.

E.OD: Excessive position fault

What it means: Under position control, the difference between the position command and the position feedback exceeded Pr.427 Excessive level error.^[3][4][5]

Also on: FR-A800, FR-E800 (same code and name)

Likely causes

• Encoder mounting direction different from the parameter setting
• Load too large
• Pr.427 or Pr.369 set wrong

First checks, in this order

1. Check that the encoder mounting direction matches the parameters.
2. Reduce the load.
3. Check Pr.427 and Pr.369.

E.EP: Encoder phase fault

What it means: The rotation command differs from the motor direction the encoder reports.^[3][4][5]

Also on: FR-A800, FR-E800 (same code and name)

Likely causes

• Encoder cable wired wrong
• Pr.359 Encoder rotation direction set wrong

First checks, in this order

1. Check the encoder wiring.
2. Check Pr.359.

E.11: Opposite rotation deceleration fault

What it means: During torque control under Real sensorless vector control, the motor did not reverse when the speed command changed direction, which caused an overload.^[3][4][5]

Also on: FR-A800, FR-E800 (same code and name)

Likely causes

• Rotation direction switched during torque control under Real sensorless vector control

First checks, in this order

1. Avoid switching rotation direction during torque control under Real sensorless vector control.
2. Contact Mitsubishi service if it persists.

E.OP3: Communication option fault

What it means: A communication line error occurred in the plug-in communication option (fitted in option connector 3 on the FR-A700).^[3][4]

Also on: FR-A800 (E.OP1 to E.OP3)

Likely causes

• Wrong option function settings
• Plug-in option not seated
• Broken communication cable or missing terminating resistor

First checks, in this order

1. Check the option function settings.
2. Seat the plug-in option firmly.
3. Check the communication cable and the terminating resistor.

SL: Speed limit indication (output during speed limit)

What it means: During torque control, motor speed went above the speed limit level.^[3][4][5]

Also on: FR-A800, FR-E800 (same code and name)

Likely causes

• Torque command larger than needed
• Speed limit level set too low

First checks, in this order

1. Reduce the torque command.
2. Raise the speed limit level.

CP: Parameter copy

What it means: Parameters were copied between an inverter of 55K or smaller and one of 75K or larger, so capacity-related settings need checking.^[3]

Likely causes

• Parameter copy between different capacity classes

First checks, in this order

1. Set again the capacity-related parameters the manual lists (for example Pr.9, Pr.30, Pr.70, Pr.80 and Pr.82).
2. Then set the initial value in Pr.989 Parameter copy alarm release.

OLC: Stall prevention (overcurrent)

What it means: FR-E800 display for current stall prevention: output current went above Pr.22 (150% at ND rating by default), so the inverter holds or lowers the frequency to avoid an overcurrent trip. The FR-LU08 LCD panel shows OL.^[5]

Likely causes

• Pr.7 or Pr.8 too short
• Pr.0 Torque boost too high
• Load too heavy or a fault in peripheral equipment
• Pr.13 Starting frequency too high

First checks, in this order

1. Increase Pr.7 and Pr.8.
2. Change Pr.0 1% at a time while watching the motor.
3. Reduce the load.
4. Try Advanced magnetic flux vector, Real sensorless vector or Vector control, or change Pr.14.
5. Raise Pr.22, or disable stall prevention with Pr.156.

OLV: Stall prevention (overvoltage)

What it means: FR-E800 display for voltage stall prevention: regenerative power during deceleration is too high, so the inverter pauses deceleration to avoid an overvoltage trip. The FR-LU08 LCD panel shows oL.^[5]

Likely causes

• Sudden speed reduction
• Regeneration avoidance function active

First checks, in this order

1. Increase Pr.8 Deceleration time.
2. Check the regeneration avoidance settings (Pr.882, Pr.883, Pr.885, Pr.886).

E.SCF: Output short-circuit

What it means: An output short circuit was detected while Pr.521 = 1. With Pr.521 = 0 (initial) a short shows as E.OC1, E.OC2 or E.OC3 instead.^[5][4]

Also on: FR-A800 (same code and name)

Likely causes

• Short circuit in the motor cable or motor

First checks, in this order

1. Find and fix the output short circuit.
2. Reset by switching the inverter power off.

E.SOT: Loss of synchronism detection

What it means: Under PM sensorless vector control, the PM motor fell out of step with the inverter.^[5][4]

Also on: FR-A800 (same code and name)

Likely causes

• PM motor overloaded
• Start command given while the motor is coasting
• Motor disconnected
• A motor other than a PM motor driven under PM control

First checks, in this order

1. Lengthen the acceleration time and reduce the load.
2. For restarts while coasting, set Pr.57 Restart coasting time to a value other than 9999.
3. Check the motor connection.
4. Perform offline auto tuning for the PM motor.