Perth's Mitsubishi Electric fault code lookup
Mitsubishi Electric fault codes decoded
79 codes covered — what each one means, the likely cause, and whether it's worth trying something yourself before booking. Compiled from Mitsubishi Electric documentation.
Mitsubishi Electric systems report faults three ways: as blink counts on the indoor unit's operation indicator (MSZ wall splits), as two-character check codes on wired controllers (P, E, U and F codes), and as 4-digit codes on newer PAR-40/41 controllers and MELCloud. All are covered below for the residential MSZ, MXZ and ducted ranges.
How to find your Mitsubishi Electric fault code
MSZ wall splits — count the indicator blinks
- 1 The wireless remote shows no code. When a fault trips, the indoor fan stops and the OPERATION INDICATOR lamp blinks in bursts.
- 2 Count the blinks between the 2.5-second pauses, and watch at least two full cycles to be sure of the count.
- 3 A continuous 0.5-second on/off blink with no pause means an indoor–outdoor signal fault.
- 4 On multi (MXZ) systems: if the lamp stays on for 3 seconds before the burst, the fault is in the outdoor unit; no 3-second lead-in means it's the indoor unit.
Wired controllers (ducted and optional on splits)
- 1 The check code appears directly on the controller screen.
- 2 Older PAR-21/PAR-31 controllers show two-character codes (P-codes indoor, E-codes communication, U/F-codes outdoor).
- 3 Newer PAR-40/41 backlit controllers, central controllers and MELCloud show 4-digit codes instead — the two systems map to each other (U2 = 1102, P5 = 2502).
Careful: recall mode uses a different table
- 1 These units memorise faults, and a technician can replay them using the failure-mode recall function.
- 2 The recall blink counts are NOT the same as the live blink counts — the same number means different things in each mode.
- 3 If a count doesn't match what you're seeing, check whether the unit is in normal operation or recall mode.
Mitsubishi Electric fault code tables
MSZ wall splits (wireless remote) — operation indicator blink patterns
| Code | What it means | Likely cause | What to do |
|---|---|---|---|
| Continuous blink (0.5s on/off) | Indoor unit is not receiving the serial signal from the outdoor unit (indoor–outdoor communication fault) | Miswiring of the indoor–outdoor connecting cable, no power to the outdoor unit, tripped breaker, or interference on the signal line | Try this first Switch the system off at the isolator/breaker for 2 minutes, then restore power and retry; if the lamp resumes blinking, book a technician |
| 2 blinks (then 2.5s off) | Indoor coil thermistor or room temperature thermistor fault | Sensor short or open circuit detected during operation | Book a service |
| 3 blinks | Indoor fan motor fault — no speed feedback signal from the fan | Fan motor failure, jammed line-flow fan, or indoor PCB fault | Book a service |
| 4 blinks | Indoor control system fault | Indoor electronic control PCB cannot read its nonvolatile memory — board failure | Book a service |
| 5 blinks | Discharge temperature fault — the compressor discharge thermistor read above 116°C and the compressor stopped. It restarts once the discharge temperature falls to 100°C or less. | Compressor or inverter fault, closed stop valve, or power supply problem | Switch off & call |
| 6 blinks | Outdoor thermistor fault | An outdoor sensor short or open circuit during compressor operation | Book a service |
| 7 blinks | Heat sink or PCB over-temperature — the inverter fin thermistor exceeded roughly 75–86°C (varies by model series) and the unit shut down to protect the electronics. | Inverter PCB or outdoor control PCB memory error | Book a service |
| 14+ blinks | Other outdoor unit abnormality | Closed stop valve, 4-way valve fault or other outdoor fault — a technician identifies the detail via the failure-mode recall function | Book a service |
| Upper lamp lit + lower lamp blinking | MXZ multi-split mode conflict — this indoor unit is asking for a different mode (COOL vs HEAT) than the unit that started first | Indoor units on one MXZ outdoor unit set to opposing modes; the first unit running has priority | Try this first Set all indoor units on the multi system to the same mode (all cooling or all heating) — this is normal behaviour, not a fault |
MXZ multi-split outdoor faults — indoor lamp flash counts (failure-mode recall, MXZ-F series)
| Code | What it means | Likely cause | What to do |
|---|---|---|---|
| 2 flashes | Outdoor power system fault — overcurrent protection tripped 3 times within a minute of compressor start | Compressor wiring fault, inverter fault or closed stop valve | Switch off & call |
| 3 flashes | Outdoor thermistor fault (discharge, defrost, ambient, fin, PCB or heat-exchanger sensor) | Sensor short or open circuit while the compressor runs | Book a service |
| 4 flashes | Compressor overcurrent — excessive current into the inverter power module | Compressor winding fault, loose compressor connector or closed stop valve | Switch off & call |
| 5 flashes | Discharge temperature too high (over ~115°C) | Refrigerant shortage/leak or expansion valve (LEV) fault | Switch off & call |
| 6 flashes | High-pressure protection — outdoor heat exchanger over 70°C in cooling (or indoor gas pipe in heating) | Blocked outdoor coil, restricted airflow, closed stop valve or refrigerant circuit problem | Try this first With the unit off, clear leaves and debris from around the outdoor unit and clean the indoor filters; if it recurs, book a technician |
| 7 flashes | Inverter fin or PCB over-temperature (fin ~88–90°C) | Blocked airflow around the outdoor unit, outdoor fan problem or sensor fault | Try this first Ensure the outdoor unit has clear airflow — remove debris and anything stacked around it — then power cycle; recurrence needs a technician |
| 8 flashes | Outdoor fan motor fault — failed 3 times within 30 seconds of starting | Fan motor failure or obstruction in the fan | Book a service |
| 9 flashes | Nonvolatile memory data cannot be read properly, OR a power module fault (short circuit in the power module output or compressor winding). | Inverter or outdoor control PCB failure | Book a service |
| 10 flashes | Low discharge temperature protection | Refrigerant overcharge/circuit problem or expansion valve (LEV) fault | Switch off & call |
| 11 flashes | The inverter's DC bus-bar voltage cannot be detected normally, or the compressor phase currents cannot be detected normally. | Wiring between outdoor boards, power supply voltage problem or PCB failure | Book a service |
| 14–17 flashes (model-dependent) | Refrigerant system abnormality — closed stop valve or air in the circuit detected (2F series); LEV/drain pump fault at 15 flashes on 3F/4F series | Stop valve left closed after installation, gas leak, air trapped in the refrigerant circuit, or indoor LEV/drain pump fault | Switch off & call |
Wired controller check codes — indoor unit (P / E / F codes: ducted SEZ & PEA, any unit on a PAR controller)
| Code | What it means | Likely cause | What to do |
|---|---|---|---|
| E0 / E3 | Remote controller transmission error | Wiring/connection fault between controller and indoor unit, or wrong master/slave (grouping) settings | Book a service |
| E1 / E2 | Remote controller control board error | Faulty wired controller board | Book a service |
| E4 | Remote controller signal receiving error | Comms fault indoor unit → controller; addressing error on grouped/twinned systems | Book a service |
| E5 | Remote controller transmission error (controller not receiving reply from indoor unit) | Controller wiring fault, wrong main/sub (master/slave) controller setting, duplicated addressing in grouped systems, or electrical interference | Try this first |
| E6 / E7 | Indoor/outdoor unit communication error | Outdoor unit powered before indoor, electrical noise on S1/S2/S3 (classically a condensate pump wired into the terminals), loose connecting cable | Try this first Power the whole system off at the breaker for 2 minutes and restore — this clears most one-off interference trips; if E6/E7 returns, book a technician |
| E8 / E9 / EE | Indoor–outdoor communication failure (transmitting error) | S2/S3 signal wiring fault, units powered up in the wrong order, or interference from pumps wired into the terminals | Try this first Power cycle at the breaker for 2 minutes (this also re-sequences indoor-then-outdoor power-up); recurrence needs a technician |
| EA / Eb / EC | Indoor–outdoor wiring and start-up faults: EA = miswiring (too many indoor units connected, 4 or more); Eb = miswiring (wires reversed or disconnected); EC = start-up time over (the indoor and outdoor units didn't finish their communication handshake in time — not a compressor fault). | Wrong/loose inter-connecting cables, wrong cable size, noise interference; EC = unit failed to initialise after power-up | Book a service |
| Ed | Serial communication error between outdoor control board and inverter board | Loose inter-board connectors, failed inverter or control PCB in the outdoor unit (4-digit equivalent: 0403) | Book a service |
| F4 | 49C connector open (compressor discharge thermal protector circuit open) | Discharge thermo protector tripped or its connector disconnected/broken on the outdoor board | Book a service |
| Fb | Indoor unit control system error | Indoor PCB memory error or board failure | Book a service |
| P1 | Intake (return air) sensor error | Room/return-air thermistor TH1 open or short circuit, or unplugged from the board | Book a service |
| P2 / P9 | Pipe (liquid or 2-phase pipe) sensor error | Indoor coil thermistor TH2/TH5 open or short circuit | Book a service |
| P4 | Drain sensor error | Drain float sensor open/short circuit or disconnected | Book a service |
| P5 | Drain pump error — high condensate level detected | Drain pump failure or a blocked condensate drain line | Try this first Check the condensate drain outlet outside for kinks or blockage and clear any debris; if water has backed up or the code returns, book a technician |
| P6 | Freezing (cooling) / overheating (heating) safeguard operation on the indoor coil | Reduced airflow — dirty filters, blocked return air, fan problem — or a refrigerant charge issue | Try this first Clean the return-air filters, make sure all supply/return grilles are open, then power cycle for 2 minutes; recurrence needs a technician |
| P8 | Pipe temperature error — no temperature change detected at the indoor coil during operation | Most commonly refrigerant leakage; can also be a mis-mounted thermistor or the outdoor unit having tripped | Switch off & call |
| PA | Forced compressor stop due to a water leakage abnormality. | Compressor protection triggered (e.g. water leak / abnormal condition detected) | Switch off & call |
| PL | Refrigerant circuit abnormal | Leak, blockage or valve problem in the refrigerant circuit | Switch off & call |
| Pb (PB) | Indoor unit fan motor error | Indoor fan motor or motor drive circuit failure, jammed blower wheel, or loose fan motor connector — very common on ducted SEZ/PEAD units | Book a service |
| UE | Abnormal high pressure — stop/ball valve closed | Service valves left closed after installation or service, or a blockage in the refrigerant circuit | Book a service |
| UL | Abnormal low pressure | Refrigerant undercharge/leak, closed valve, or low-pressure sensor fault | Book a service |
Wired controller check codes — outdoor unit (U / F codes)
| Code | What it means | Likely cause | What to do |
|---|---|---|---|
| F1 / F2 / F7 | Power phase fault (reverse phase or missing L3 phase) — three-phase ducted systems | Phases connected in the wrong order or an open phase in the supply; possible board fault | Switch off & call |
| F3 / F5 / F9 | Protection device circuit open (63L low-pressure switch, 63H high-pressure switch, or two or more devices) | Pressure switch disconnection or contact failure; possible outdoor board fault | Book a service |
| U1 / Ud | Abnormal high pressure (63H switch operated) or overheating safeguard | Outdoor fan failure, blocked/dirty outdoor coil, system blockage, or blocked indoor filters when heating | Try this first Turn the unit off, clear leaves/debris around the outdoor unit, clean indoor filters, then power cycle; if it trips again, book a technician |
| U2 | Abnormally high discharge temperature, the compressor thermal protector (49C) has operated, or the system is low on refrigerant. | Insufficient refrigerant (leak), faulty thermistor or extreme operating conditions | Switch off & call |
| U3 | Discharge thermistor fault | Sensor open/short circuit or disconnected | Book a service |
| U4 | Outdoor unit thermistor fault | An outdoor sensor open/short circuit or disconnected | Book a service |
| U5 | Abnormal inverter heat-sink temperature | Lack of airflow around the outdoor unit/heat sink, or a faulty sensor | Try this first With power off, clear anything blocking airflow around the outdoor unit, then power cycle; recurrence needs a technician |
| U6 | Compressor overcurrent / power module abnormality | Compressor electrical fault or inverter power module failure | Switch off & call |
| U7 | Superheat abnormality due to low discharge temperature | Refrigerant overcharge, expansion valve (LEV) fault or faulty discharge thermistor | Book a service |
| U8 | Outdoor unit fan safeguard stop | Fan motor fault or fan obstructed | Try this first With power off at the breaker, check nothing (leaves, sticks, ice) is fouling the outdoor fan and clear debris; if the fan still won't run, book a technician |
| U9 / UH | Over/under-voltage, abnormal synchronous signal to main circuit, or current sensor error | Power supply voltage problem, wiring fault or inverter board failure | Switch off & call |
| UF | Compressor overcurrent interruption — compressor locked | Seized/locked compressor | Switch off & call |
| UP | Compressor overcurrent interruption | Compressor drawing excessive current — electrical or mechanical compressor fault | Switch off & call |
4-digit check codes (newer PAR-40/41 controllers, MELCloud & central controllers)
| Code | What it means | Likely cause | What to do |
|---|---|---|---|
| 0403 | Serial communication error (outdoor control board to inverter board) | Board-to-board wiring/connector fault or failed inverter/control PCB — one of the most common outdoor PCB faults technicians see | Book a service |
| 1102 | High compressor discharge temperature (equivalent to U2) | Refrigerant shortage or discharge thermistor fault | Switch off & call |
| 1301 | Abnormal low pressure detected before/at startup | Refrigerant leak or shortage, closed service valve, or pressure sensor fault | Book a service |
| 1302 | High pressure fault (equivalent to U1) | Blocked outdoor coil, fan failure, closed valve or system blockage | Try this first Clear debris around the outdoor unit and clean indoor filters, then power cycle for 2 minutes; if it recurs, book a technician |
| 1500 / 1501 | Refrigerant charge abnormality — 1500 overcharge, 1501 shortage (low discharge superheat / compressor shell temperature) | Incorrect charge at installation or a refrigerant leak — the classic 'low on gas' fault customers ask about | Book a service |
| 2500 | Water leakage / drain sensor submergence detected (drain fault while unit is stopped) | Blocked condensate drain or failed drain pump letting water rise in the tray — risk of ceiling water damage on ducted units | Switch off & call |
| 2502 | Drain pump fault — water detected in the drip tray (equivalent to P5) | Drain pump failure or blocked condensate drain | Try this first Check the condensate drain outlet for blockage and clear it; if water remains or the code returns, book a technician |
| 2503 | Drain sensor fault (equivalent to P4) | Drain float sensor open/short circuit | Book a service |
| 4102 / 4115 | Power supply abnormal — open phase or supply fault | Loss of a phase, blown fuse, wiring or PCB problem | Switch off & call |
| 4116 | Fan motor abnormal | Indoor fan motor or board fault | Book a service |
| 4220 | Abnormal bus voltage in the inverter | Mains supply voltage problem or inverter board fault | Switch off & call |
| 4230 | Heatsink (inverter) overheat protection | Blocked outdoor coil, failed outdoor fan, or debris restricting airflow over the inverter heatsink — clear leaves/debris and restore clearance first | Try this first |
| 4240 | Overload (compressor overheat) protection activated | Dirty coils/filters, over- or under-charge, or high ambient causing sustained compressor overload | Book a service |
| 4250 | Overcurrent protection — inverter power module or compressor (equivalent to U6/UF) | Compressor lock or inverter IPM failure | Switch off & call |
| 4255 | Fan motor abnormality (fan RPM error) | Failed DC fan motor or fan drive circuit, seized bearing, or obstructed fan — a frequent 'outdoor fan not spinning' complaint | Book a service |
| 5101 – 5105 | Thermistor faults at indoor/outdoor unit (5104 discharge = U3, 5105 outdoor = U4) | A temperature sensor open/short circuit or disconnected from the board | Book a service |
| 5110 | Heatsink temperature thermistor (THHS) fault | Open/short circuit in the inverter heatsink sensor or its connector on the outdoor board | Book a service |
| 5201 / 5202 | High-pressure (63H) / low-pressure (63L) switch circuit open (equivalent to F5/F3) | Pressure switch disconnection or contact failure | Book a service |
| 5300 / 5301 | Current sensor (ACCT) error | Open/short circuit in the compressor current sensor or inverter board fault; can also flag when the compressor draws no current (wiring/compressor fault) | Book a service |
| 5701 | Drain float switch fault (loose connector or float switch tripped) | Condensate safety float switch activated by rising water, or its connector loose on the indoor board — seen on ducted units with safety trays | Book a service |
| 6201 / 6202 | Remote controller board fault (6201 flash memory error, 6202 clock IC error) | Failed PAR wired controller internal board — replace the controller | Book a service |
| 6600 | Duplicate address (address overlap) on the communication line | Two units or controllers set to the same address after installation or board replacement — readdress and reset power | Book a service |
| 6607 / 6608 | Communication error — no acknowledgement/response on the transmission line | Transient noise interference, wiring fault or loss of transmission voltage | Try this first Power the outdoor unit off for 30 seconds to 2 minutes and restore power; if the code returns, book a technician |
| 6831 – 6834 | MA remote controller communication fault | Controller wiring on TB15 loose, cable run too long, too many controllers, or noise interference | Book a service |
| 6840 / 6841 / 6844 / 6845 / 6846 | Indoor–outdoor communication/wiring faults (equivalent to E8/E9/EA/EB/EC) | Miswired or loose connecting cables, wrong cable spec, power-up sequence, or start-up time-out | Try this first Power cycle the whole system at the breaker for 2 minutes; persistent codes mean a wiring fault that needs a technician |
No matching code found.
Meanings vary by series and some codes are model-specific — call 0434 951 341 with the code and your model number and we'll decode it.
Reference compiled from Mitsubishi Electric service and operation documentation. Codes and meanings are provided as general guidance for the Australian residential range and can differ between model series; no affiliation with Mitsubishi Electric is implied.
Tell us the code when you book — diagnosis starts before we arrive
Air conditioning service and repairs across Perth from $220 inc GST — all brands, splits and ducted. Quoting the fault code gives us a head start on where to look; we then test and confirm the actual fault on site before any part is ordered, so you never pay for a part you didn't need.
Frequently Asked Questions
How do I read the blinking light on my Mitsubishi Electric split?
Count the blinks of the operation indicator between the 2.5-second pauses, watching at least two full cycles to be sure. A continuous blink with no pause means an indoor–outdoor signal fault. On multi (MXZ) systems, a 3-second lit period before the burst means the fault is in the outdoor unit.
Is this the same as Mitsubishi Heavy Industries?
No. Mitsubishi Electric and Mitsubishi Heavy Industries are different companies with different code systems — MHI's E-number codes don't apply to these units and vice versa. Check the badge on your indoor unit before using either table.
What's the difference between the 2-character and 4-digit codes?
They're the same faults in two conventions: older PAR-21/PAR-31 controllers show codes like U2 or P5, while newer PAR-40/41 controllers, central controllers and MELCloud show 4-digit equivalents (U2 = 1102, P5 = 2502). Both tables are on this page.
My blink count doesn't match anything in the table — why?
Almost certainly because the unit is in failure-mode recall rather than live operation — the two modes use different blink numbering. Series also differ (MSZ-GE vs MSZ-AP, MXZ-2F vs MXZ-3F/4F). Call 0434 951 341 with your model number and the count and we'll decode it.
Perth homeowners have trusted us for 10+ years. Here's what they say.
Real five-star reviews from Perth homeowners — see why locals choose Otter Air for air conditioning and electrical work.
See all reviews