57 Mitsubishi AC error codes + troubleshooting (FULL LIST)

Table of Contents

Today we are please to offer the complete list of Mitsubishi aircon error codes. No matter you want to troubleshoot your own Mitsubishi air conditioner or troubleshooting for clients, this mitsubishi ac troubleshooting guide will help.

Let’s get started with Mitsubishi electric air conditioner error codes first.

Mitsubishi error code 0403 (Serial communication error)

Cause : The fault occurs when there is a communication issue between PCB’s in the outdoor unit. If the model number is YGMA, YHMA, YJMA, YKMA or YLMA then the issue can be between the main board and inverter board or main board and fan board.

Check Procedure :

Check for poor connections and broken wiring between the boards. If the model number is YGMA, YHMA, YJMA, YKMA or YLMA, check the error detail code using the dip-switches section of the app to determine which PCB’s the transmission fault is with. If the detail code is 1, then the issue is between the main board and inverter board.

If the detail code is 5 then the issue is between the main board and fan board. Then check for poor connections between the PCB’s.

Mitsubishi error code 0403

Technical Support Notes:

If there are no loose connections on either PCBs and the voltages are good then the Fan or Inverter PCB is usually at fault. This is not normally a problem with the main PCB.

Correct testing should allow you to identify which of the 2 boards is the cause. The online document link will take you to the document library where Service Handbooks can be viewed.

Mitsubishi error code 0900 (Test run)

Cause : Test operation dipswitch on the Lossnay circuit board has been set ON.

Check Procedure :

Check the position of Dipswitch SW2-1 on the main control board. If test is not required then set the dip switch to OFF.

Mitsubishi error code 1102 (Discharge temperature fault)

Cause : Insufficient cooling of the compressor caused by lack of refrigerant or a restriction in the refrigerant circuit, high ambient running conditions or airflow problems on either indoor or outdoor unit (depending on running mode), over heating of compressor through increased friction (compressor beginning to seize), faulty thermistor reading.

Check Procedure :

Use the testing dip switches in the app and check the system running pressures/temperatures and determine if the system is short of gas or if there is a restriction in the circuit – a restriction may show frosting where refrigerant expands, this could be a blocked strainer, faulty expansion valve operation or perhaps moisture in the system.

Check compressor running current -if higher than expected this could show a compressor issue.

Mitsubishi error code 1301 (Low pressure fault)

Cause : Possible refrigerant leak. Restriction or blockage in refrigerant circuit causing low side pressure to drop. Problem with pressure sensor reading incorrectly.

Check Procedure :

Check the system standing pressure for a complete gas loss.

Use the Testing dip switches in the app and compare system gauge pressure to Low Pressure Sensor reading – If the pressure sensor is faulty it will read 0.0 bar even though there is pressure in the system.

Technical Support Notes :

Using the testing dip switches check the system running pressures/temperatures to determine if the system is short of gas or if there is a restriction/blockage in the circuit.

For refrigerant circuit diagram click the link below and type unit model number into the document library search box

Mitsubishi error code 1302 (High pressure fault)

Cause : High pressure faults are commonly caused by a blocked condenser coil, faulty fan motor, a restriction of airflow on indoor units in heating mode or a blockage/restriction in the pipework.

Check Procedure :

Check outdoor fan operates correctly, ensure no restriction of airflow across indoor/outdoor coils such as clogged filters. Use the testing dip switches in the app to check system running pressures/temperatures – This may help highlight any blockages or restrictions in the refrigerant circuit such as faulty solenoid valves or check valves stuck closed.

Technical Support Notes :

If the you reset the unit and the fault generates straight away (without running) then the high pressure switch or sensor may be at fault. Measure the switch for continuity (normally closed) and use the dip switches to check the pressure sensor reading against your gauge pressure.

Mitsubishi error code 1500 (Refrigerant overcharge)

Cause : Normally caused by excessive refrigerant returning to the outdoor unit which over-cools the compressor. System is either over-charged or there are valves operating incorrectly allowing refrigerant to ‘flood’ back to the compressor.

Check Procedure :

Check correct reading of high pressure sensor and discharge thermistor. Check for excessive refrigerant returning to the outdoor unit through overcharge of gas, incorrect valve operation in the system or issue with linear expansion valve (LEV) control in BC Box or Indoor unit

Technical Support Notes :

An indoor LEV stuck open can be an obvious cause to this issue. Try running the system in full cooling and then checking if there is an indoor unit that performs much better than the others.

Mitsubishi error code 2500 (Drain sensor submergence)

Cause : Water pump off/faulty. Water flow rate too slow. Float switch faulty.

Check Procedure :

Check water pump. Check water flow rate. Check continuity of float switch.

Mitsubishi error code 2500
Drain sensor submergence

Mitsubishi error code 2502 (Drain pump fault)

Cause : The indoor unit drain float has detected a high water level in the drip tray.

Check Procedure :

Check the indoor drip tray for water. If there is excessive water then there may be an issue with the internal pump or drains. If the tray is dry or hasn’t enough water to lift the float switch then check the float switch for continuity. If the switch is lifted the circuit should be made. If the switch is down then the circuit should be open.

Mitsubishi error code 2502

Technical Support Notes :

The internal lift pump is not activated by the float switch, the pump is activated when cooling mode is selected. This fault is triggered by the float switch circuit closing.

Mitsubishi error code 2503 (Drain sensor fault)

Cause : The drain sensor is open/short circuit.

Check Procedure :

If the drip tray is clear then check the resistance of the drain sensor as an open circuit or short circuit can cause the fault.

Mitsubishi error code 2503

Technical Support Notes :

Check the wiring diagram to see if the indoor unit has a float switch or sensor. If the wiring diagram shows a float switch and not a sensor check the dip switch settings for the unit model you are working on.

Mitsubishi error code 2600 (Water leakage)

Cause : Water leak from pipes on humidifier.

Check Procedure :

Check that water does not leak from pipes in humidifier.

Mitsubishi error code 4102 (Open phase)

Cause : Missing main phase.

Check Procedure :

Check power supply and noise filter for correct 3 phase, check wiring and fuses.

Mitsubishi error code 4106 (Transmission power supply fault)

Cause : Transmission (M-Net), incorrect wiring.

Check Procedure : Check wiring, high current, incorrect voltage on transmission line and/or M-Net board. Make sure M-net transmission wiring is daisy chained.

Mitsubishi error code 4115 (Power supply signal sync error)

Cause : Incorrect power supply, blown fuses or possible faulty PCB.

Check Procedure :

Check mains power is correct, check the fuses, and connections PCB.

Mitsubishi error code 4116 (RPM error/Motor error)

CauseCheck Procedure
Faulty connection of a fan.Check the connection for the fan motors.
Faulty connection of the leads between the Control board and the Power board.Check the connections between the Control board and the Power board.
Model selection switch SW6 is set incorrectly.Confirm that the model selection switch SW6 is set correctly for the model.
Ambient temperature in which the unit is located is high.Check the temperature around the Lossnay.
Fan isn’t fixed correctly.Confirm that the fan motors are fixed securely.
Deformed centrifugal fan.Check that the centrifugal fan is clear of debris.
Centrifugal fan has foreign objects in or around it.Replace the fan motor.
Fan motor fault.Replace the circuit board.
Circuit board fault.Check the connections of the reactor (TB3-4) and check the resistance of it.
Faulty connection of the reactor.To identify which fan the issue is with, check the LED flashing sequence and contact After Sales Technical Support.
Mitsubishi error code 4116

Mitsubishi error code 4220 (Abnormal bus voltage)

Cause : Low mains power supply, diode fault.

Check Procedure :

Check mains supply. Check DC bus voltage coming from diode.

Mitsubishi error code 4225 (Low bus voltage)

Cause : Incorrect mains supply or fan board fault.

Check Procedure :

Check mains power is ok and there is at least 300vdc at the diode stack.

Mitsubishi error code 4225

Technical Support Notes :

Check to see if the error led is lit on the fan board, this is a good indication that the fan board is the issue.

Mitsubishi error code 4230 (Heatsink overheat protection)

Cause : Blockage in air passage of inverter heatsink, Inverter board failure, inverter fan failure.

Check Procedure :

Check blockages in air duct failure of INV fan or failure of thermistor.

Mitsubishi error code 4240 (Overload protection)

Cause : If high current is detected for more than 10mins.

Check Procedure :

Check inverter balance. Reduced airflow through heat sink.

Mitsubishi error code 4250 (Over current protection)

Cause : High amps drawn by the compressor or an issue with the inverter.

Check Procedure :

Carry out an inverter output test to check if the inverter is working correctly. Use the “inverter testing guide” in the City Multi section of the APP. If the inverter is ok then check the compressor windings for a short or open circuit.

Technical Support Notes :

Use the service dipswitches on the outdoor unit to get the detail code which will indicate if the issue is with the inverter or compressor.

Mitsubishi error code 4255 (Outdoor fan error)

Cause : Grounding fault of fan motor or fan board fault.

Check Procedure :

Check the voltage on CNVDC on the fan. This should be a high DC voltage around 580vdc.

Also check the fan motor windings for an open or short circuit.

Technical Support Notes :

Use the service dipswitches on the outdoor unit to get the detail code which will indicate if the issue is with the fan board or fan motor.

Mitsubishi error code 4260 (Heatsink overheat protection at startup)

Cause : Reduced airflow through heat sink.

Check Procedure :

Fan motor problem. THHS thermistor problem.

Mitsubishi error code 5101 (Temperature sensor fault)

CauseCheck Procedure
Faulty thermistor – dead short/open circuit.The fault can be related to indoor or outdoor so check the fault code for address of unit in fault first.
Damaged thermistor cable or poor connection to PCB.Check connection of thermistor on PCB and thermistor wiring.
PCB incorrectly reading thermistor value.Unplug thermistor and test resistance value.

If all the above are correct then replace the PCB.

Technical Support Notes :

Correct reading of thermistor can be determined using Thermistor Value Look Up in the app.

Check whether the thermistor is for reading High temperature e.g .Discharge, or Normal running e.g. Ambient/Liquid, to determine which range to check against.

Mitsubishi error code 5102 (Return Air thermistor fault)

Cause : The circuit board cannot read the thermistor correctly

Check Procedure :

Check the connection onto the circuit board.

Check the resistance of the thermistor.

Replace the thermistor.

Replace the circuit board.

Mitsubishi error code 5110 (Outdoor inverter heatsink thermistor error)

Cause : Reduced airflow through inverter heatsink.

Check Procedure :

Open/short circuit sensor, disconnected from PCB.

Mitsubishi error code 5110

Technical Support Notes :

On the YGM-A series this can be either THHS1 or THHS5. To find out which it is you will need to check the inverter detail code using SW1 on the control board. Turn on SW1 dips 1,2,5,6,8 and look at the display for the code to be retrieved. THHS1=01 and THHS5=05.

Mitsubishi error code 5201 (Pressure sensor fault)

Cause : PS1 Pressure fault.

Check Procedure :

Check pressure reading using the dipswitches on the outdoor. Check connection of PS3 on PCB.

Mitsubishi error code 5301 (Current sensor fault)

Cause : ACCT or DCCT sensor error.

Check Procedure :

Check inverter error details, check resistance of current sensor, check connections of sensors.

Mitsubishi error code 5701 (Loose float switch connector)

Cause : The indoor unit internal float switch connector has detected an open circuit.

Check Procedure :

Check the float switch is operating correctly. If the switch is down then the switch should be open.

Also check for external pumps wired in across the fail safe connection.

Mitsubishi error code 5701

Technical Support Notes :

This fault normally occurs when an external pump is wired in across the fail safe connections, (CN4F/CN31) and the external pump has failed. Or the connection is loose.

Mitsubishi error code 6201 (Remote controller issue)

Cause : The remote controller is faulty

Check Procedure :

Replace the controller.

Mitsubishi error code 6600 (Address overlap)

Cause : There is more than one unit with the same MNET address or two or more devices are addressed the same.

Check Procedure :

Check the address set on each device on the same MNET network.

Check address settings on outdoors, indoors, BC boxes and remote controllers to see if two have the same address settings.

Mitsubishi error code 6600

Technical Support Notes :

This is only caused when two items are addressed the same. If they all look like they are set correctly power the system down and spin the address dials all the way around to confirm they are clicked into the position they should be. If the system also has a 6607 fault this could indicate where the repeat address has occurred.

Mitsubishi error code 6601 (Polarity setting error)

Cause : No voltage or short circuit on M-Net transmission line TB7.

Check Procedure :

Check TB7 connections on outdoors and central controllers. Check for voltage on TB7. Check cable size and spec.

Mitsubishi error code 6602 (Transmission processor hardware error)

CauseCheck Procedure
Noise interference. Polarity problem on TB7.Check M-Net connection on TB7 and central controller. Check cable size/spec.
Controller where the error originally occurred is defective.Check the controller where the error occurred and replace if required.
Lossnay circuit board is defective.Replace the circuit board.
Mitsubishi error code 6602

Mitsubishi error code 6603 (Transmission line bus busy error)

Cause :

Power is supplied to the same transmission cable from two or more power supply units.

The power supply unit is connected to TB3 side of the power supply expansion units.

The power supply units connected to the indoor and outdoor transmission cables.

Check Procedure :

Adjust the wiring of the power supply unit.

Mitsubishi error code 6603

Mitsubishi error code 6606 (Communication fault)

Cause :

Poor connection of MNET terminals.

MNET cables have been terminated whilst the unit is powered.

Malfunction of the unit PCB.

Check Procedure :

Check that the MNET cables have been terminated correctly.

Reset power to the system.

Inspect the Control Board for damage.

Replace the Control Board.

Mitsubishi error code 6606

Mitsubishi error code 6607 (No ACK error)

Cause :

Lossnay has no power.

Lossnay address has been changed.

Transmission cable is in excess of 500m.

Transmission cable is not securely terminated.

Check Procedure :

Check the power supply to the Lossnay.

Check the Lossnay address.

Check the cable length.

Check the cable termination.

Technical Support Notes :

The 6607 fault should also give you the address of the item in fault, if it does check power and M-Net voltage at the item.

If no address is given with the fault code then this is referred to as a “ghost fault”, this is caused when something with an address is physically removed from the system without being deleted first.

Mitsubishi error code 6608 (No response error)

Cause :

When using multiple Lossnay units, the Main/Sub switch has not been set.

Interference on the transmission line.

Cable length is in excess of 500m.

Transmission cable is not securely connected.

Multi core cable is being used for multiple uses and causing interference.

Check Procedure :

Isolate power and set the lead unit to Main using SW1 and the remaining units to Sub.

Check and repair cable terminations.

Check the length of the transmission cable.

Check that the cable used is as specified.

Mitsubishi error code 6608

Mitsubishi error code 6831 (MA controller signal reception error)

Cause : MA controller being wired into the M-Net. Wrong cable size/spec.

Check Procedure :

Check where remote is wired to, check cable length no bigger than 500 meters, check connection and type of cable used, check R/C not set Sub on field settings.

Mitsubishi error code 6831

Mitsubishi error code 6832 (MA controller comms fault)

Cause : MA controller being wired into the M-Net. Wrong cable size/spec.

Check Procedure : Check where remote is wired to, check cable length no bigger than 500 meters, check connection and type of cable used, check R/C not set Sub on field settings.

Mitsubishi error code 6832

Mitsubishi error code 6833 (MA controller comms fault)

Cause : MA controller being wired into the M-Net. Wrong cable size/spec.

Check Procedure :

Check where remote is wired to, check cable length no bigger than 500 meters, check connection and type of cable used, check R/C not set Sub on field settings.

Mitsubishi error code 6833

Mitsubishi error code 6834 (MA controller signal reception error)

Cause : MA controller being wired into the M-Net instead of the remote terminals. Wrong cable size/spec.

Check Procedure :

Check where remote is wired to, check the cable length is no bigger than 500 meters, check connection and type of cable being used, check R/C not set Sub on field settings.

Mitsubishi error code 6834

Technical Support Notes :

This is usually caused when an M-Net controller is replaced with an MA controller. Make sure if you have an M-Net remote it is wired into the M-Net terminals and if you have an MA remote it is wired into the remote controller terminals.

Mitsubishi error code 7100 (Total capacity error)

Cause :

The total indoor unit capacity exceeds the outdoor unit allowable capacity.

On a PURY outdoor you are allowed up to 150% of its capacity.

On a PUHY/PUMY outdoor you can have up to 130% of its capacity.

Check Procedure :

Add up all the capacities of the indoor units and check they don’t exceed the outdoor unit capacity.

Also check the capacity dip switches on the indoor and outdoor unit are set correctly.

Technical Support Notes :

This fault can be caused when the system is comprised of two outdoor units piped together and power is lost to one of the outdoors.

Mitsubishi error code 7101 (Capacity code setting error)

Cause : SW2 set wrong on indoors, SW5 dips set wrong on YHM-A outdoor, SW3-10 on older kit.

Check Procedure :

Capacity dips on indoor and outdoor units.

Mitsubishi error code 7101

Mitsubishi error code 7102 (Wrong number of connected units)

Cause : The outdoor unit is not seeing any indoor units or it is seeing more than the allowable value.

Check Procedure :

Check voltage on M-Net, power to the BC box, check dip switches are set correctly on the BC box and the model type of BC box is correct for the system.

Technical Support Notes :

Check the voltage on the M-Net at the outdoor unit (it should be 29vdc). If there is no voltage then power down and remove the M-Net and check the terminals again. If you then get 29vdc then there is an issue somewhere on the M-Net, a loose connection or short maybe.

Mitsubishi error code 7105 (Address setting error)

Cause : OC or BC addressed wrong.

Check Procedure :

Check address setting on OC and BC.

Mitsubishi error code 7106 (Attribute setting error)

Cause : GUF unit being used on City Multi system.

Check Procedure :

Make sure SW3-1 setting is on, on the GUF.

Mitsubishi error code 7110 (Signal transmission error)

Cause : Loose or misswiring of TB3 or TB7. SW5 dip 7 not set on outdoor. Transmission booster turned off.

Check Procedure :

Check M-Net connections, dipswitches on outdoors.

Mitsubishi error code 7111 (Remote controller sensor fault)

Cause : SW1 – 1 on and no controllers fitted or faulty remote controller.

Check Procedure :

Check SW1 – 1 on the indoor unit if no remote controllers fitted.

Mitsubishi error code 7111

Mitsubishi error code 7113 (Function setting error)

Cause :

More than 1 unit in the group is set to as the Main Lossnay (SW5-10 ON)

The group contains two or more units with the same address.

The Lossnay that is set to the Main, has not been set to the lowest unit address in the group.

The MA remote controller for the air conditioner (Mr.Slim or City Multi) is connected to the Lossnay.

Incorrect wiring of the remote controller terminals.

The Lossnay LGH-RVX is in the same group as a Lossnay LGH-RX5.

The model selection switch SW6 is not set correctly.

Check Procedure :

Check the SW5-10 setting on the Lossnays in the same group and confirm that there is only one set to Main(ON)

Check the address settings of the Lossnay units.

Change the remote for a PZ-61DR-E.

Check that the wiring of the remote terminals and the MNET terminals.

The LGH-RVX and the LGH-RX5 cannot be used in the same group.

Confirm that the SW6 setting is correct for the model.

Mitsubishi error code 7117 (Model setting error)

Cause : SW5 set wrong on the outdoor or wrong resistors fitted.

Check Procedure :

Check dips, resistors and thermistors.

Mitsubishi error code 7130 (Incompatible unit combination)

Cause : Check split with MAC 399 wired onto the TB5 line not the TB7.

Check Procedure :

Check M-Net wiring on systems.

Now, let’s proceed with Mitsubishi heavy air conditioner error codes. If you want to learn more about Mitsubishi heavy vs electric, please refer to our previous guide for more info.

Mitsubishi error code E1 (Remote controller communication issue)

Cause : Faulty controller or poor wiring connection/abnormal voltage to the Remote controller

Check Procedure :

Check the remote controller wiring connection onto the FTC terminals and ensure there is 12vdc down to the Remote controller.

Make sure LED2 is lit on the FTC Control board

Mitsubishi error code E2 (Remote controller transmitting error)

Cause : Incorrect wiring of remote or incorrect dip switch setting if units are grouped.

Check Procedure :

Check unit addressing if grouped or check remote is only wired to master indoor unit.

Mitsubishi error code E3 (Remote controller communication/receiving error)

Cause :

Incorrect settings on SW1 switches at the outdoor unit.

Poor connection or wiring of the remote controller.

Check Procedure :

Check for 12vdc down to the controller and make sure LED 2 is lit on the FTC board

Check the SW1 dips switches on the outdoor unit are set correctly.

Mitsubishi error code E5 (Remote controller communication/receiving error)

Cause :

Remote controller incorrectly wired or the controller does not have the correct 12vdc supply.

Incorrect settings on SW1 switches at the outdoor unit.

Check Procedure :

Check for 12vdc down to the controller and make sure LED 2 is lit on the FTC board.

Check the SW1 dips switches on the outdoor unit are set correctly.

Mitsubishi error code E6 (Indoor to outdoor communication fault)

Cause : Loss or no communication between the FTC and outdoor Ecodan. Poor connection of the interconnecting cable or not the correct 12-24vdc fluctuating voltage between S2 and S3.

Check Procedure :

Reset power supply to both indoor FTC and outdoor Ecodan. Power back up the indoor first then the outdoor. Check interconnecting cable connections and voltages. Check indoor FTC LEDs.

Technical Support Notes :

The most common cause of an E6 fault is external noise interference caused by condensate pumps being wired into S1 & S2. If a pump is wired in to S1 & S2 and you have an E6, then try disconnecting the pump and repowering the system to see if it works.

Mitsubishi error code E7 (Comms failure indoor to outdoor)

Cause : Mis-wiring of indoor to outdoor cable. System powered up incorrectly.

Check Procedure :

Check for pumps wired in, Check indoor isolator, Repower in correct sequence i.e. indoor then outdoor.

Mitsubishi error code E8 (Indoor to Outdoor communication error)

Cause : Loss or no communication between the FTC and outdoor Ecodan. Poor connection of the interconnecting cable or not the correct 12-24vdc fluctuating voltage between S2 and S3.

Check Procedure :

Reset power supply to both indoor FTC and outdoor Ecodan. Power back up the indoor first then the outdoor. Check interconnecting cable connections and voltages. Check indoor FTC LEDs.

Mitsubishi error code E9 (Indoor to outdoor communication error)

Cause :

Loss or no communication between the FTC and outdoor Ecodan. Poor connection of the interconnecting cable or not the correct 12-24vdc fluctuating voltage between S2 and S3.

SW8-3 set to OFF when independent power supplies are used.

Check Procedure :

Reset power supply to both indoor FTC and outdoor Ecodan. Power back up the indoor first then the outdoor. Check interconnecting cable connections and voltages. Check indoor FTC LEDs.

Power down complete system and set SW8-3 to ON before powering the FTC before the Ecodan.

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