Mitsubishi AC Error Codes and Fixes

Mitsubishi manufactures high-quality air conditioners for residential and commercial purposes. The company has an extensive range of service centers throughout India.

Usually, Mitsubishi Electric engages authorized third-party service providers for attending to AC installations and troubleshooting. So, users are advised to note the error codes displayed on the remote controller or the IDU when they encounter problems with the Mitsubishi AC. It allows the service technicians to diagnose the faults quickly and accurately, saving considerable time.

Mitsubishi ACs are available in various models. Generally, the error codes vary from one model to the other. Nevertheless, we shall discuss the standard error codes usually observed by residential users.

Mitsubishi AC Error Codes and Fixes

Users should not attempt to repair Mitsubishi AC themselves because the circuits inside the appliance can be complicated. It is advisable to call the authorized Mitsubishi service technician if they encounter any problem with the Mitsubishi AC.

Cleaning the filters is the only activity users should do. We recommend cleaning the AC filters every month to prevent dust accumulation. It affects the appliance’s functioning and also results in higher power consumption.

Here are the standard error codes observed in Mitsubishi ACs

A6 – Communication Error

This error can occur when the AC PCB loses communication with the communication processor. It can be a wiring problem or a loose connection issue. A faulty PCB can also result in a communication error. The AC technician takes appropriate action.

EA – Wiring Issues

The EA error occurs when there is a wiring or a connection issue. For example, the wires could have snapped, or there could be a loose connection problem. As a result, you can experience noise interference. The AC technician checks and repairs the wiring accordingly.

EB – Wiring problems

The EB error is similar to the EA error code. A problem with the wiring or loose interconnecting cables can cause this fault. Though it is an electrical fault, it is advisable to get the AC inspected by an authorized Mitsubishi technician.

EC – Start Up error

The unit does not start after switching on the power. The unit displays the EC error code signifying that the start-up time is over. There can be a timer error. You can try to switch off the unit and restart it. If it does not start, the AC technician is the right person to deal with the problem.

ED – Serial communication error

The error signifies a lack of proper communication between the IDU and ODU or between the IDU and ODU PCBs. The lack of communication in the M-NET system can also cause this error. Users can check whether the ODU PCB connector is disconnected. It can be a wiring issue. The lack of internet connectivity on smart ACs can also cause this error. So, checking the broadband connectivity can resolve the problem.

EF – Non-defined

Some Mitsubishi ACs exhibit the error code EF. It is a non-defined error usually signifying noise interference or lack of power supply to the outdoor unit. In addition, it can be a transmission problem. Usually, switching off the AC and restarting it can resolve the issue. However, if it persists, you must contact the AC technician.

E0, E1, E2, E3, E4, and E5 – Remote controller communication error

All these errors are remote controller issues. Reconnecting the remote controller to the AC power system should resolve the issue. The AC technician must resolve this issue. It can also happen due to the supply of an incompatible remote controller. Changing the remote controller can solve these problems.

E6 – Miscommunication between the indoor and outdoor units

Check the wiring between the IDU and ODU. Try switching the AC off and restarting it. If it does not restart, there could be a snapped connection. The solution is to call the Mitsubishi AC technician and replace the wiring.

E7, E8, and E9 – Communication fault between the IDU and ODU

Improper wiring can cause these errors. Usually, it occurs because of connecting the wires in the wrong sequence. The AC technician should resolve this problem by re-powering the connections correctly.

FA – Installation error, 51CM connector open

Closing the 51CM connector can resolve the problem.

F1 – Installation error, Reverse phase detection.

It is an installation error where the current phases have been misconnected. Reversing the phases can resolve the problem.

F2 – Installation error, L3 phase open

The AC technician should check the power supply and open circuit protection devices.

F3 – Installation error, 63L open

This installation error requires checking the low-pressure switch for loose connections or failure.

F4 – Installation error, 49C open

Checking the inner compressor thermostat for open circuits or contact failure should resolve these problems.

F5 – Installation error, 63H open

The technician should check for the high-pressure switch for contact failure or misconnection.

F7 and F8 – Faulty Outdoor PCB

The solution is to replace the defective PCB. Usually, Mitsubishi offers warranties on the PCB. So, if the unit is under the warranty period, the company replaces it for free.

P1 – Sensor issue, TH1 fault

The P1 error code is the result of the return air thermistor failure. Replacing the sensor is the correct solution.

P2 – Sensor Issue, TH2 fault

The P2 error code signifies a faulty liquid pipe thermistor. The technician should check for disconnection or replace the defective sensor.

P4 – Sensor issue, Drain sensor failure

The P4 error code indicates drain sensor failure. Replace the sensor to rectify the problem.

P5 – Sensor failure, faulty drain pump

The P5 error code indicates a faulty drain pump. So, replacing the defective pump and reconnecting the sensor is the correct solution.

P6 – Reduced airflow

The reason for the reduced airflow can be blockages in the filter or a problem with the fan motor. Users can check the filters and clean them. If the problem persists, there could be a fan motor issue. The AC technician should intervene and check for capacitor failure. Usually, replacing the capacitor resolves the issue.

P8 – Refrigerant leakage issue

The P8 error code requires professional handling. It indicates a refrigerant leakage issue. So, users should not attempt setting it right. The correct solution is to book the service call and summon the technician. The solution is plugging the leakage and refilling the gas.

P9 – Sensor issue, TH5 thermistor open

A loose connection of the condenser or evaporator sensor TH5 can cause the P9 error code. The AC technician reconnects the sensor or replaces it if faulty.

U1 – Outdoor unit fan failure

The U1 error code signifies outdoor unit fan failure. The reason could be a blocked coil or a system blockage. Clogged filters can also cause this error code. The solution is identifying the right problem and resolving it. First, the AC technician inspects the outdoor fan for loose winding coils and capacitor issues. Then, replacing the capacitor and rewinding the fan coils can resolve the issue.

U2 – Overheated compressor

The lack of refrigerant flow can cause the compressor to overheat and display the U2 error code. Check for refrigerant and refill the gas. It should resolve the problem.

U3 – Sensor fault, discharge thermistor failure

A loose connection of the discharge thermistor can cause the U3 error code. The AC technician should reconnect the sensor or replace it.

U4 – Sensor issue, outdoor thermistor failure

An outdoor thermistor failure causes the U4 error code. The solution is to reconnect or replace the sensor.

U5 – Abnormal heat sink temperature

An overheated heat sink can cause the U5 error. The AC technician should check whether the indoor and outdoor units have a short cycle on their air ducts. Measuring the resistance value of the outdoor thermistor TH8 can resolve the issue.

U6 – Abnormal power

Excessive current supply to the compressor causes the error code U6. Check the input current voltage and install a voltage stabilizer to handle such issues.

U7 – Low discharge superheat

The solution is to check for refrigerant levels. A difference in the resistance values among terminals on the indoor and outdoor linear expansion valves can also cause this problem.

U8 – Abnormal outdoor fan speed

A faulty fan capacitor or motor can cause this problem. Technicians can check the TH3 connector on the outdoor controller board. Disconnection or a loose connection can cause this issue.  

U9 – Voltage issue

Abnormal input voltage can cause the U9 error code. Users can connect an external voltage stabilizer to rectify the issue. However, the authorized technician should check for other connected matters.

Mitsubishi Numeric Error Codes

Some Mitsubishi AC units display numerical error codes. Most numerical error codes match the alphabetical codes explained above. Nevertheless, we shall list them out for convenience. Almost all errors require the intervention of the authorized Mitsubishi AC technician to resolve the issue.

Error CodeFaultSolution
0403Serial communication errorCheck the wiring between the main board and the inverter board.
0900Test runCheck Dipswitch SW2-1 on the main control board.
1102Discharge temperature faultCheck the compressor’s running current.
1301Low-pressure faultCheck the system standing pressure for gas loss
1302High-pressure faultCheck for clogged filters or restricted coils.
1500Refrigerant overchargeCheck for the excess refrigerant returning to the ODU through overcharging.
2500Drain sensor submergeCheck water pump and water flow rate.
2502Drain pump faultCheck the float switch for continuity.
2503Drain sensor faultCheck for a short circuit and replace the sensor if damaged.
2600Water leakageCheck for water leakage on humidifier pipes.
4102Open phaseCheck power supply, wiring, and fuses.
4106Transmission power supply faultCheck wiring, input voltage, and broadband connection.
4115Power supply signal sync errorCheck mains power, fuses, and PCB connections.
4116Motor/RPM errorCheck the fan motor connections, confirm secure fixing, clear the debris, or replace the motor/circuit board.
4220Abnormal bus voltageCheck mains supply and DC bus voltage.
4225Low bus voltageCheck mains power and voltage at the diode stack.
4230Heatsink overheat protectionCheck for blockages in the air passage, inverter failure, or inverter fan faults.
4240Overload protectionCheck inverter balance and reduce airflow through the heat sink.
4250Over current protectionCheck for open and short circuits and repair them.
4255Outdoor fan errorCheck the voltage on the fan and motor windings for short circuits.
4260Heatsink overheat protection at start-upReplace the THHS thermistor if faulty.
5101Temperature sensor faultCheck for fault address code, thermistor connections, and wiring. Otherwise, replace the PCB.
5102Return air thermistor faultCheck for connection issues and thermistor resistance and replace the sensors or circuit board.
5110Outdoor inverter heatsink thermistor errorCheck for open/short circuits and disconnections from the PCB.
5201Pressure sensor failureReconnect or replace the sensors.
5301Current sensor failureReplace the sensors if faulty.
5701Loose float switch connectorCheck for correct float switch operations and external pumps.
6201Remote controller issueReplace the remote controller.
6600Address overlapMatch the address with the broadband network.
6601Polarity setting issueCheck for voltage issues and cable sizes.
6602Transmission procedure hardware errorCheck the controller and broadband connections, and replace the circuit board if required.
6603Transmission line bus busy errorCheck for faulty wiring and repair it.
6606Communication failureCheck the PCB for defects. Reset the power. If the error persists, replace the PCB.
6607No ACK errorCheck for power supply, Lossnay address, cable length, and termination.
6608No response errorCheck and repair cable termination, length, and type of cables used.
6831MA controller signal reception errorCheck the remote, cable length, types of cable, and connections.
6832MA controller comms faultCheck remote, cable length, types of cable used, and connections.
6833MA controller comms faultSame as error code 6832
6834MA controller signal reception errorSame as error code 6832
7100Total capacity errorAdd capacities of all indoor units and match them with the outdoor unit capacity.
7101Capacity code setting errorCheck for capacity dips in IDU and ODU.
7102Wrong number of connected unitsCheck for voltage on the broadband set-top box and if you have connected the correct box.
7105Address setting errorCheck the address setting on the OC and BC.
7106Attribute setting errorEnsure that the SW3-1 setting is on.
7110Signal transmission errorCheck for broadband connections.
7111Remote controller sensor faultCheck SW-1 on the IDU.
7113Function setting errorCheck the SW5-10 settings and SW6 settings.
7117Model setting errorCheck the dips, resistors, and thermistors.
7130Incompatible unit combinationCheck broadband wiring on the systems.

Final Thoughts

We advise users to contact the Mitsubishi official service center and lodge their complaints online. They should not attempt to repair their ACs by themselves. The authorized technician is the perfect person to handle problems with the AC.  

Gaurav Arvind
Gaurav Arvind
I am a software engineer by profession but blogger by passion. I have been doing blogging, reviews and writing about products for the past 3 years. I love what I do. If you can't tell me what it's made of, I won't tell you how good it is !


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