Mitsubishi Heavy Industries Air-Conditioning Europe · A niche brand in the UK. 186 codes across 2 product families, each taken from the manufacturer’s manuals. Mitsubishi Heavy Industries Air-Conditioning Europe technical support ↗
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186 codes
| Code | Meaning | Stops? | Homeowner check? |
|---|---|---|---|
| 1 | Sensor fault: BT1 outdoor sensor: No contact with the sensor (temperature sensor, outdoor) | Partly | Yes |
| 3 | Temperature limiter in indoor unit has tripped (blocks both outdoor unit and electric heater). | Yes | Yes |
| 4 | No voltage to the outdoor unit from indoor unit. | Yes | Yes |
| 5 | Too low temperature out from the condenser; occurs if alarm 70 occurs 3 times within an hour. | Yes | Yes |
| 6 | Sensor fault: BT6 hot water load: No contact with the sensor (temperature sensor, hot water charging) | Varies by model | Yes |
| 7 | Anti-freeze of heat exchanger; occurs if alarm 72 occurs 3 times within an hour. | Yes | Yes |
| 8 | Too high temperature (>90 C) on hot water sensor (BT6); blocks hot water via outdoor unit and additional heat. | Partly | Yes |
| 9 | Too high temperature (>90 C) on immersion heater sensor (BT19). | Partly | Yes |
| 10 | Too high temperature (>90 C) on flow line sensor, system 1 (BT2); heating/cooling switched off, only hot water permitted. | Partly | Yes |
| 11 | Too high temperature (>90 C) on flow line sensor, system 2. | Partly | Yes |
| 14 | Occurs if alarm 70 or 77 occurs 10 times continuously during defrost operation. | Yes | Yes |
| 16 | Occurs if alarm 78 (min flow protection) occurs 10 times continuously during defrost operation. | Yes | Yes |
| 25 | Sensor fault: BT25 external supply: No contact with the sensor (heat medium supply, external) | Partly | Yes |
| 28 | Sensor fault: BT71 external return sensor: No contact with the sensor (return line, external) | Partly | Yes |
| 30 | Sensor fault, outdoor temperature (BT1). | Partly | Yes |
| 31 | Sensor error: BT63 flow sensor: No contact with the sensor (external supply line after heater) | Varies by model | Yes |
| 32 | Sensor fault, condenser out (BT12). | Yes | Yes |
| 33 | Sensor flt: BT53 solar panel: Sensor not connected/defective (solar panel) | Varies by model | Yes |
| 34 | Sensor flt: BT54 solar: Sensor not connected/defective (solar coil) | Partly | Yes |
| 35 | Sensor flt: BT52 boiler sensor: No contact with the sensor (boiler) | Partly | Yes |
| 36 | Sensor flt: EP21-BT2 flow line sensor: Sensor not connected/defective (supply sensor extra climate system 2) | Partly | Yes |
| 37 | Sensor flt: EP22-BT2 flow line sensor: Sensor not connected/defective (supply sensor extra climate system 3) | Partly | Yes |
| 38 | Sensor flt: EP23-BT2 flow line sensor: Sensor not connected/defective (supply sensor extra climate system 4) | Partly | Yes |
| 39 | Sensor error: EQ1-BT64 cooling supply: No contact with the sensor (cooling supply line) | Partly | Yes |
| 48 | Sens flt: room sens cool oper: No contact with the sensor (cooling) | Partly | Yes |
| 56 | Erroneous serial no: The heat pump has a serial number that does not exist | Yes | Yes |
| 57 | Erroneous software: The heat pump's program and serial number do not match each other | Yes | Yes |
| 59 | Incompatible setting: Additional heat before QN10 without hot water being selected | No | Yes |
| 70 | Communication fault with PCA input: Communication with the input board (AA3) is missing | Partly | Yes |
| 71 | Communication fault with PCA base: Communication with PCB (AA2) is missing | Varies by model | Yes |
| 72 | Low pressure below 0.65 MPa in cooling mode (auto reset above 0.83 MPa or condenser out above 14 C). | Partly | Yes |
| 73 | Outdoor temperature below 0 C and operating mode does not permit heating (resets above 1 C). | Partly | Yes |
| 73-91 | Com. err. PCA Accessory: Communication with the accessory board is missing | Partly | Yes |
| 75 | Too high current output from the house (resets when current decreases). | Partly | Yes |
| 77 | Low pressure below threshold according to water temperature during defrost; defrost forcibly finished and heating restarts. | Partly | Yes |
| 78 | Temperature difference BT12-BT3 bigger than predetermined value during defrost; defrost finished and heating restarts. | Partly | Yes |
| 96-99 | Com. err. RMU: Communication with the room unit is missing | Partly | Yes |
| 107 | Sensor flt: BT7 HW sens top: The input for the sensor receives an unreasonably high or low value for longer than 2 seconds | No | Yes |
| 130-135 | Com flt PCA accessory: Communication with the accessory board for climate systems 5-8 has been missing for 15 seconds | Partly | Yes |
| 151-152 | Sen flt: CL-BTxx: Pool sensor input unreasonable for longer than 5 seconds | Partly | Yes |
| 156 | Low lp cool: 5 repeated alarms for low pressure within 4 hours | Yes | Yes |
| 157 | Low lp cool: The low pressure transmitter in the outdoor unit is showing a value too low (R410A manual: protection against freezing in water HX during cooling) | Yes | Yes |
| 162 | High condenser out temperature: Condenser out has reached max permitted temperature (self-resetting) | Yes | Yes |
| 163 | High condenser in temperature: Condenser in has reached max permitted temperature (self-resetting) | Yes | Yes |
| 170 | Communication fault with PCA input: Communication fault has occurred to the input board AA3 | No | Yes |
| 171 | Communication fault with PCA base: A temporary communication fault has occurred to PCB AA2 | Yes | Yes |
| 173-178 | Com. err. acc.: Communication fault has occurred to the accessory board | Partly | Yes |
| 180 | Anti-freeze: Frost protection active (outdoor below 3 C, no heating permitted, supply below calculated) | Partly | Yes |
| 181 | Problems at periodic increasing: Periodic hot water increase did not reach the stop temperature in 5 hours | No | Yes |
| 182 | Load monitor active: Measured power consumption for at least one phase exceeds the fuse size specified in the menu | Partly | Yes |
| 183 | Defrosting: Defrosting in progress (not an alarm, an operating status) | Partly | Yes |
| 187 | Com. err. acc.: Communication fault has occurred - step controlled additional heat | Partly | Yes |
| 188 | Com. err. PCA accessory: Communication fault has occurred - solar heating | Partly | Yes |
| 191 | Com. err. PCA accessory: Communication fault has occurred - hot water comfort | Partly | Yes |
| 193 | Com flt PCA accessory: Communication fault to EME20M has occurred 3 times in a row | Partly | Yes |
| 206 | Com flt PCA accessory: Communication with the accessory board for HW comfort has been missing for 15 seconds | Partly | Yes |
| 208 | Com flt PCA accessory: Communication with the accessory board for external additional heat has been missing for 15 seconds | Partly | Yes |
| 209 | Com flt PCA accessory: Communication fault - step controlled additional heat | Partly | Yes |
| 211 | Cpr not running: The compressor has not been running for 36 hours even if needed | No | Yes |
| 212 | Cmpr has not been running for a week: Compressor has not been running for a week | Partly | Yes |
| 218 | The compressor's rotor is blocked: Compressor is blocked | Yes | Yes |
| 220 | High pressure alarm: The high pressure switch (63H1) has deployed 5 times within 60 minutes or has been deployed for 60 minutes continuously | Yes | Yes |
| 221 | Low pressure alarm: Too low value on the low pressure sensor 3 times within 60 minutes | Yes | Yes |
| 223 | Motor protection alarm: Communication between the control board and the communication board is interrupted (there must be 22 VDC at CNW2 on PWB1) | Yes | Yes |
| 224 | Fan alarm from heat pump: Deviations in the fan speed in the outdoor unit | Yes | Yes |
| 225 | Mixing up sensor flow/return: The return is hotter than the supply | Yes | Yes |
| 226 | Stove monitor activated: Stove monitor activated | No | Yes |
| 227 | Sensor fault from heat pump: Sensor not connected/defective | Yes | Yes |
| 228 | Failed defrosting: Failed 10 consecutive defrostings | Yes | Yes |
| 229 | Short operating times for compr.: Operation was stopped from the indoor unit section after less than 5 minutes | Yes | Yes |
| 230 | Hot gas alarm: Temperature deviations on the discharge sensor, 2 times within 60 minutes or continuous for 60 minutes | Yes | Yes |
| 232 | Low evaporation temp: 5 repeated alarms for low evaporation temperature within 4 hours | Yes | Yes |
| 251 | Com. err. MODBUS: Communication with the accessory (MODBUS40M) has been missing for 15 seconds | Partly | Yes |
| 261 | High HWX temp: Temperature deviation on the heat exchanger sensor (Tho-R1/R2) 5 times within 60 minutes or continuously for 60 minutes | Yes | Yes |
| 262 | Inv. err.: Power transistor too hot: IPM shows FO (fault output) signal 5 times in 60 minutes | Yes | Yes |
| 263 | Inv. err.: Voltage from the inverter outside the parameters 4 times within 30 minutes | Yes | Yes |
| 264 | Communication error with inverter: Communication between inverter board and control board/PCB interrupted | Yes | Yes |
| 265 | Inv. err.: Continuous deviation on power transistor for 15 minutes | Yes | Yes |
| 266 | Low refrig.: Insufficient refrigerant detected at start-up in cooling (1 min after start BT15 must have decreased 15K compared to BT3) | Yes | Yes |
| 267 | Inv. err: Failed start for compressor | Yes | Yes |
| 268 | Inv. err.: Overcurrent, inverter A/F module | Yes | Yes |
| 270 | Compr. preheat in progress: Preheating of compressor in progress | Yes | Yes |
| 271 | Cold outd air, heating mode: The outside temperature is outside the outdoor unit's working range (R410A manual: 'Lw otd tmp', BT28 below permitted value) | Yes | Yes |
| 272 | Warm outd air, heat. mode: The outdoor temperature is outside the outdoor unit's working range (R410A manual: 'High otd tmp') | Yes | Yes |
| 273 | Short run times twice in a row: Set hot water levels cannot be reached | Partly | Yes |
| 274 | Compressor limited by load monitor: The load monitor prevents the compressor from running at desired power | No | Yes |
| 275 | Compressor long term. restr. by load monitor: The load monitor prevents the compressor from running at desired power | No | Yes |
| 277 | Sensor fault from heat pump: Input for sensor Tho-R (evaporator) has received an unreasonably high or low value 3 times within 40 minutes | Yes | Yes |
| 278 | Sensor fault from heat pump: Input for sensor Tho-A (outdoor sensor) unreasonable 3 times within 40 minutes | Yes | Yes |
| 279 | Sensor fault from heat pump: Input for sensor Tho-D (discharge) unreasonable 3 times within 40 minutes | Yes | Yes |
| 280 | Sensor fault from heat pump: Input for sensor Tho-S (suction gas) unreasonable 3 times within 40 minutes | Yes | Yes |
| 281 | Sensor fault from heat pump: Input for sensor LPT (low pressure sensor) unreasonable 3 times within 40 minutes | Yes | Yes |
| 282 | Com flt PCA accessory: Temporary comm. fault, 4-pipe active cooling accessory | Partly | Yes |
| 292 | Sen flt: BT74 cool/heat sensor: Sensor BT74 on the AUX input is not connected/defective | Partly | Yes |
| 294 | Incompatible heat pump: The outdoor air heat pump is not compatible | Yes | Yes |
| 301 | Slave heat pump #1 comm. err.: Communication with slave heat pump 1 has been missing for 15 seconds | Partly | Yes |
| 302-308 | Comm. err. slave 2-8: Communication with slave heat pump 2-8 has been missing for 15 seconds | Partly | Yes |
| 319-321 | Comm flt with EB10x -GP12: Communication with the accessory board for GP12 (EB103/4, EB105/6, EB107/8) missing for 15 seconds | Partly | Yes |
| 334 | Max. incoming temp. exceeded: BT3 higher than 65 C in heating mode | Partly | Yes |
| 336-339 | Sen flt: EP4x-BT2 supply temp sens.: Sensor not connected/defective (extra climate systems EP44-EP47) | Partly | Yes |
| 341 | Recurring safety defr.: Alarm from outdoor unit | Yes | Yes |
| 342 | Low water temperature in: Low temperature in during cooling operation | Yes | Yes |
| 343 | Low temp water out: Low temperature out during cooling operation (R410A manual: also during tank defrost) | Yes | Yes |
| 344 | Recurring low pressure: Alarm from outdoor unit | Yes | Yes |
| 346 | Recurring high pressure: Alarm from outdoor unit | Yes | Yes |
| 347 | Temp high press: Temporary high pressure alarm | Yes | Yes |
| 349 | Sens flt: EQ1-BT74: The cooling accessory room sensor has no contact with the control module | Partly | Yes |
| 350 | Sensor fault on BT50 room sensor: Sensor not connected/defective | No | Yes |
| 354-355 | Failed sensor calibration: Delta BT3-BT12 is greater than 2K after calibration | Partly | Yes |
| 361-368 | Sensor fault EPxx, BT3 return line sensor: Sensor BT3 (return) not connected/defective in one of the climate systems | No | Yes |
| 372 | Perm. com. error pool 2: Communication with Pool 2 has been missing for 15 seconds | Partly | Yes |
| 400 | Unspecified fault: Unspecified faults | Partly | Yes |
| 403 | Sensor fault from PCA 154: Sensor fault in the outdoor unit (R410A manual PSC012D085CD: incoming water sensor BT3) | Yes | Yes |
| 404 | Sensor fault from PCA 154: Sensor fault in the outdoor unit (R410A manual: high pressure heating / low pressure cooling sensor BP4) | Yes | Yes |
| 412 | Sensor fault from PCA 154: Sensor fault in the outdoor unit (R410A manual: outgoing water sensor BT12) | Yes | Yes |
| 415 | Sensor fault from PCA 154: Sensor fault in the outdoor unit (R410A manual: fluid pipe sensor BT15) | Yes | Yes |
| 418 | Low temp water out: Flow protection defrosting (R410A manual: anti-freeze protection water HX during defrost) | Partly | Yes |
| 419 | Freeze prot. exch. defr.: Frost protection exchanger defrosting | Partly | Yes |
| 420 | Temp. com. fault w. inverter: A temporary communication fault in the inverter has occurred | Partly | Yes |
| 421 | Com. fault w. inverter: A temporary communication alarm has occurred 3 times within 2 hours or has been active for 1 hour | Yes | Yes |
| 422 | Inverter alarm type II: Compressor stop due to protection mode | Yes | Yes |
| 424 | Triggered pressure switch: Temporarily triggered pressure switch | Yes | Yes |
| 425 | Triggered pressure switch: Permanent pressure switch alarm | Yes | Yes |
| 426 | Temp. safety stop inv.: A temporary internal fault in the inverter has occurred | Yes | Yes |
| 427 | Safety stop inverter: A temporary fault in the inverter has occurred 2 times within 60 minutes | Yes | Yes |
| 428 | Temp. safety stop inv.: A temporary internal fault in the inverter has occurred | Yes | Yes |
| 429 | Safety stop inverter: A temporary internal fault in the inverter has occurred 3 times within 2 hours | Yes | Yes |
| 430 | Temp. high mains voltage: Phase voltage to the inverter too high | Yes | Yes |
| 431 | High mains voltage: The phase voltage in the inverter has been too high 3 times within 3 hours or continuously for 1 hour | Yes | Yes |
| 432 | Inverter alarm type I: Phase voltage to inverter too low | Yes | Yes |
| 433 | Inverter alarm type I: The phase voltage in the inverter has been too low 3 times within 3 hours or continuously for 1 hour | Yes | Yes |
| 436 | Temp. mains disturb.: A temporary inverter fault has occurred | Yes | Yes |
| 437 | Mains disturbance: A temporary fault has occurred 3 times within 2 hours or has been continuous for 1 hour | Yes | Yes |
| 438 | Temp. overheated inverter: Inverter temporarily reached max working temperature due to poor cooling | Yes | Yes |
| 439 | Overheated inverter: Inverter temporarily reached max working temperature due to poor cooling 3 times within 2 hours or continuously for 1 hour | Yes | Yes |
| 440 | Inverter alarm type II: Max. current in has been temporarily too high | Yes | Yes |
| 441 | Inverter alarm type II: Max current in has been temporarily too high 3 times within 2 hours or continuously for 1 hour | Yes | Yes |
| 442 | Temp. overheated inverter: Temporarily overheated inverter | Yes | Yes |
| 443 | Overheated inverter: Inverter temporarily reached max working temperature due to poor cooling 3 times within 2 hours or continuously for 1 hour | Yes | Yes |
| 444 | Temp. inverter protection: The inverter detects a temporary fault | Yes | Yes |
| 445 | Inverter protection: The inverter detected a temporary fault within 10 seconds after compressor start, 5 times in a row | Yes | Yes |
| 446 | Temp. phase drop: Compressor phase missing | Yes | Yes |
| 447 | Phase drop: Compressor phase has been missing 3 times within 2 hours or continuously for 1 hour | Yes | Yes |
| 448 | Failed compressor start: Compressor does not start when required | Yes | Yes |
| 449 | Failed compressor starts: The compressor has not started when required 3 times within 2 hours | Yes | Yes |
| 452 | Temp. high curr load cmpr: The current out from the inverter to the compressor has been too high | Yes | Yes |
| 453 | High curr load cmpr: Output current from the inverter to the compressor temporarily too high 3 times within 2 hours or continuously for 1 hour | Yes | Yes |
| 454 | Temp high pow load cmpr: Power from inverter too high | Yes | Yes |
| 455 | High power load compressor: Power output from the inverter too high 3 times within 2 hours or continuously for 1 hour | Yes | Yes |
| 460 | Inverter alarm type II: Current into the inverter temporarily too high | Yes | Yes |
| 461 | Inverter alarm type II: Current to the inverter too high 3 times within 2 hours or continuously for 1 hour | Yes | Yes |
| 502 | Compressor speed too low: Compressor speed below the lowest permitted speed | Yes | Yes |
| 503 | Compressor speed too low: The compressor speed is below the lowest permitted speed | Partly | Yes |
| 505 | Inverter has earth fault: Inverter has earth fault | Partly | Yes |
| 506 | Mains voltage outside inv. work. range: The mains frequency has been outside of the inverter's working range | No | Yes |
| 507 | Mains voltage outside inv. work. range: The mains frequency has lost contact with the mains network | No | Yes |
| 508 | Inv. lost contact with the mains: The inverter has lost contact with the mains network | No | Yes |
| 509 | High ambient temp. at inverter: Ambient temperature at the inverter is too high | No | Yes |
| 510 | The inverter has high DC voltage: The inverter has high DC voltage | Partly | Yes |
| 523 | Low flow defrosting: Low flow during defrosting | Partly | Yes |
| 572-575 | Sensor fault in BT50 room sensor: Sensor fault BT50 in RMU 1-4 | Partly | Yes |
| 580 | Cold outd air, cooling mode: The outdoor temperature at the outdoor unit is outside its working range | Yes | Yes |
| 581 | Warm outd air, cool. mode: The outdoor temperature at the outdoor unit is outside its working range | Yes | Yes |
| 582-588 | Low flow defrosting: Low flow during defrosting in one of EB102-EB108 | Partly | Yes |
| 900 | Country not selected: Country not defined | No | Yes |
| 995 | External alarm: An alarm has occurred according to selected function on AUX input | No | Yes |
| 996 | Blocked: Additional heat externally blocked | Partly | Yes |
| 997 | Blocked: The compressor is externally blocked | Yes | Yes |
| 998 | Starts: Display/installation has restarted | No | Yes |
| E5 | Communication between the outdoor unit and indoor unit is not made. | Yes | Yes |
| E35 | Temperature deviation on the heat exchanger sensor (Tho-R1/R2) five times within 60 minutes or for 60 minutes. | Yes | Yes |
| E36 | Temperature deviation on the hot gas sensor (Tho-D) two times within 60 minutes or for 60 minutes. | Yes | Yes |
| E37 | Sensor fault, heat exchanger in outdoor unit (Tho-R). | Yes | Yes |
| E38 | Sensor fault, outdoor air sensor in outdoor unit (Tho-A). | Yes | Yes |
| E39 | Sensor fault, hot gas in outdoor unit (Tho-D). | Yes | Yes |
| E40 | The high pressure switch (63H1) is activated 5 times within 60 minutes or continuously for 60 minutes. | Yes | Yes |
| E42 | Voltage from the inverter outside the parameters four times within 30 minutes (troubleshooting chart titled 'E42 - Current cut'). | Yes | Yes |
| E45 | Communication between PCB for inverter and control PCB broken. | Yes | Yes |
| E47 | Inverter A/F module over current. | Yes | Yes |
| E48 | Deviations in the fan speed in outdoor unit (fan speed <=100 rpm 5 times within 60 min stops compressor). | Yes | Yes |
| E49 | Too low value on the low pressure sensor 3 times within 60 minutes. | Yes | Yes |
| E51 | Continuous deviation on power transistor for 15 minutes (also shown as E41). | Yes | Yes |
| E53 | Sensor fault, suction gas in outdoor unit (Tho-S). | Yes | Yes |
| E54 | Sensor fault, low pressure sensor in outdoor unit. | Yes | Yes |
| E57 | Insufficient refrigerant is detected at initial start-up in cooling mode. | Yes | Yes |
| E59 | Compressor fails to start up 14 times (7 patterns x 2 times). | Yes | Yes |