Mitsubishi MR. Slim air conditioner error codes

Trouble shooting for Mitsubishi air conditioners based on the results of self-diagnostics.
The modern air conditioners from Mitsubishi have a very developed self-diagnostics system, and when the control system detects an error, it blocks the operation of the entire device and displays a cause of faulty condition.
The control system of the Mitsubishi air conditioners reports that an error occurred by blinking of a light-emitting diode on the surface of the internal (or external) unit. When a particular error of an air conditioner is detected, light-emitting diodes blink in a certain order, which corresponds with a particular error. If the control system of an air conditioner detects more than one error, the error with the highest priority is displayed first and then all the following errors are displayed
After completing installation and the wiring and piping of the indoor and outdoor units, check for refrigerant leakage, looseness in the power supply or control wiring, wrong polarity, and no disconnection of one phase in the supply.

Mitsubishi error codes air conditioning malfunction

P1  Intake sensor error
P2 P9 Pipe (Liquid or 2-phase pipe) sensor error
E6 E7 Indoor/outdoor unit communication error
P4 Drain sensor error
P5  Drain pump error
PA Forced compressor error
P6  Freezing/Overheating safeguard operation
EE  Communication error between indoor and outdoor units
P8  Pipe temperature error
E4  Remote controller signal receiving error
Fb  Indoor unit control system error (memory error, etc.)
E0 E3 Remote controller transmission error
E1 E2 Remote controller control board error

For details, check the LED display of the outdoor controller board.

E9  Indoor/outdoor unit communication error (Transmitting error) (Outdoor unit)
UP  Compressor overcurrent interruption
U3, U4  Open/short of outdoor unit thermistors
UF Compressor overcurrent interruption (When compressor locked)
U2  Abnormal high discharging temperature/49C worked/insufficient refrigerant
U1 Ud Abnormal high pressure (63H worked)/Overheating safeguard operation
U5  Abnormal temperature of heat sink
U8 Outdoor unit fan safeguard stop
U6  Compressor overcurrent interruption/Abnormal of power module
U7 Abnormality of super heat due to low discharge temperature
U9  UH Abnormality such as overvoltage or voltage shortage and abnormal synchronous signal to main circuit/ Current sensor error.

Mitsubishi Mr.Slim A-control air conditioning error code list

Display of remote controller

Code EA

Error detail Mis-wiring of indoor/outdoor unit. exceed the number of indoor unit connection.
Inspected unit Outdoor.

Code Eb
Error detail Mis-wiring of indoor/outdoor unit. (mis-wiring disconnection)
Inspected unit Outdoor.

Code EC
Error detail Start-up time over
Inspected unit Outdoor.

Code E6
Error detail Indoor/outdoor unit transmission error (signal receiving error).
Inspected unit Indoor.

Code E7
Error detail Indoor/outdoor unit transmission error (transmitting error).
Inspected unit Indoor.

Code E8
Error detail Indoor/outdoor unit transmission error (signal receiving error).
Inspected unit Outdoor.

Code E9
Error detail Indoor/outdoor unit transmission error (transmitting error).
Inspected unit Outdoor.

Code E0 Error detail Remote control transmission error (signal receiving error)
Inspected unit Remote control

Code E3
Error detail Remote control transmission error (transmitting error)
Inspected unit Remote control.

Code E4
Error detail Remote control transmission error (signal receiving error)
Inspected unit Indoor.

Code E5
Error detail Remote control transmission error (transmitting error)
Inspected unit Indoor.

Code EF
Error detail M-NET transmission error
Inspected unit Indoor and outdoor.

Code Ed
Error detail Serial transmission error
Inspected unit Outdoor.

Code P1
Error detail Abnolmality of room temperature thermistor (TH1).
Inspected unit Indoor.

Code P2
Error detail Abnormality of pipe temperature themistor/liquid (TH2).
Inspected unit Indoor.

Code P4
Error detail Abnomarlity of drain sensor (DS)
Inspected unit Indoor.

Code P5
Error detail Malfunction of drain-up machine.
Inspected unit Indoor.

Code P6
Error detail Freezing/overheating protection detect.
Inspected unit Indoor.

Code P8
Error detail Abnormality of pipe temperature.
Inspected unit Indoor.

Code P9
Error detail Anormality of pipe temperature thermistor/condenser/evaporator (TH5)
Inspected unit Indoor.

Code F1
Error detail Reverse phase detection.

Code F2
Error detail L3 open phase detection.

Code F3
Error detail 63L connector open.

Code F4
Error detail 49C connector open.

Code F9
Error detail Connector 2 or more open.

Code FA
Error detail L2-phased open phase or 51CM connector open.

Code F7
Error detail Reverse phase detection circuit (p.c.board) fault.

Code F8
Error detail Input circuit fault.

Code U2
Error detail Abnormal high discharging temperature.

Code U2
Error detail Inner thermostat (49C) operation.

Code U1
Error detail Abnormal high pressure (high pressure swicth 63H worked)

Code U1
Error detail Direct cut operation.

Code UE
Error detail High pressure error (ball valve closed)

Code UL
Error detail Abnormal low pressure.

Code Ud
Error detail Over heat protection

Code U6
Error detail Compressor over current (overload) cut off.

Code UA
Error detail Compressor over current (terminal relay operation).

Code UF
Error detail Compressor over current (start-up locked) cut off.

Code UF
Error detail Compressor over current (operating locked) cut off.

Code UH
Error detail Current sensor error.

Code U3
Error detail Discharge thermistor short/open.

Code U4
Error detail Outdoor thermistor short/open.

Mitsubishi Mr.Slim K-control air conditioning error codes

Display of remote controller

LED E0
Diagnosis of malfunction Transmitting/receiving signal error.
Inspected unit Indoor.

LED P1
Diagnosis of malfunction Intake air sensor abnormal.
Inspected unit Indoor.

LED P2
Diagnosis of malfunction Pipe sensor abnormal.
Inspected unit Indoor.

LED P4
Diagnosis of malfunction Drain sensor abnormal.
Inspected unit Indoor.

LED P5
Diagnosis of malfunction Malfunctioning of the drain overflow protecting mechanism.
Inspected unit Indoor.

LED P6
Diagnosis of malfunction Abnomality of the coil frost/overheating protection mode.
Inspected unit Indoor.

LED P3
Diagnosis of malfunction System error (transmitting/receiving signal).
Inspected unit Indoor.

LED P7
Diagnosis of malfunction System error (address)
Inspected unit Indoor.

LED P8
Diagnosis of malfunction Outdoor unit malfunction
Inspected unit Outdoor.

Mitsubishi Mr.Slim air conditioning K-control PUH-EK

Outdoor unit

LED ON = Operation status
LED Flash = Check code diplay

LED LD1
LED ON Compressor directive
LED Flash Reverse phase detect

LED LD2
LED ON Heating directive
LED Flash Open phase detect

LED LD3
LED ON During 63H1 operation
LED Flash Pipe sensor short/open

LED LD4
LED ON Compressor ON
LED Flash High pressure swicth (63H2) operation.

LED LD5
LED ON Outdoor fan ON
LED Flash Over current relay (51CM) operation.

LED LD6
LED ON 4-way valve ON
LED Flash Thermal swicth (26C) operation.

LED LD7
LED ON Bypass valve ON
LED Flash Thermistor (TH3) overheat protection.

LED LD8
LED ON Crankcase heater ON
LED Flash Devective input.

Mitsubishi Mr. Slim AC Error Codes

Membrane type remote controllers

Check codeDiagnosis of malfunctionCauseCheck points
EOSignal transmitting/receiving error

(Indoor controller does not respond to remote controller signal)
During individual unit control

1) Bad contact of transmission wire

2) Signal transmitting/receiving circuit is abnormal.
1) Check the transmission wire.

2) Check with another remote controller. If “EO” is still indicated, replace the indoor controller board.

If other check code appears. replace the original remote controller.
P1Abnormality of room temperature thermistor (RT1)1) Bad contact of thermistor

2) Damaged thermistor
1) Check the thermistor.

2) Measure the resistance of the thermistor.

Normal resistance should be as follows.

32°F····15kΩ 86°F·····4.3kΩ

50°F······9.6kΩ 104°F·····3.0kΩ

68°F······6.3kΩ

If the resistance is normal, replace the indoor controller board.
P2Abnormality of indoor coil thermistor (RT2)1) Bad contact of thermistor

2) Damaged thermistor
1) Check the thermistor.

2) Measure the resistance of the thermistor.

Normal resistance should be as follows.

32°F····15kΩ 86°F·····4.3kΩ

50°F······9.6kΩ 104°F·····3.0kΩ

68°F······6.3kΩ

If the resistance is normal, replace the indoor controller board.
P3Signal transmission error

(Remote controller does not respond to indoor controller signal)
1) Bad contact of transmission wire

2) Signal transmitting/receiving circuit is abnormal.

3) Wrong operation due to noise

wave emitted by other appliances
1) Check the transmission wire.

2) Check with another remote controller.

If “P3” is still indicated, replace the indoor board.

If other check code appears, replace the original remote controller.

3) Short-circuit between 1 and ➁ of CN40 and attach CN40 to the following units.

● Second unit in twin control

● Second and third units in triple control

● Sub units in group control
P4Abnormality of drain sensor1) Bad contact of transmission wire

2) Damaged thermistor
1) Check the connector.

2) Measure the resistance of the thermistor ➃ - ➄.

As for the normal resistance, refer to the case of P1.

If the resistance is normal, replace the indoor controller board.
P5Malfunction of drain pump1) Malfunction of drain pump

2) Damaged drain sensor
1) Check the drain pump.

2) ● Check the drain sensor.

● Check the drain sensor heater. Normal resistance should be 82Ω.

If the resistance is normal, replace the indoor controller board.
P6Coil frost protection is working.1) Short cycle of air cycle

2) Dirty air filter

3) Damaged fan

4) Abnormal refrigerant
1) Clear obstructions from the air cycle.

2) Clean the air filter

3) Check the fan.

4) Check the refrigerant temperature.
P7System error1) Wrong address-setting

2) Signal transmitting/receiving circuit of remote controller is abnormal.

3) Wrong SW6-setting
1) Check the address-setting.

2) Check with another remote controller. If check code other than “P7” appears, replace the original remote controller.

3) Check SW6 setting.
P8Abnormality in outdoor unit1) Wrong wiring of indoor/outdoor connecting wire

2) Reversed phase

3) Protection device is working

4) Damaged outdoor coil thermistor
1) Check the indoor/outdoor connecting wire.

2) Change the connection of electric wiring.

3) Check the protection device.

4) Measure the resistance of the outdoor coil thermistor. If the resistance is normal, replace the outdoor controller board.