Error Code Library
Mitsubishi Air Conditioner Error Codes
A short code on the controller or a blinking lamp on the indoor unit is your system telling you why it stopped. This guide to Mitsubishi air conditioner error codes explains what the usual ones mean, how to read them on your model, and which simple checks are safe before you book a licensed technician anywhere in Australia.
Start Here
Which Mitsubishi Do You Actually Own?
Before you look up any code, check the badge. Two separate manufacturers sell air conditioners under the Mitsubishi name in Australia. Mitsubishi Electric and Mitsubishi Heavy Industries share a heritage, yet they design their own systems, controllers and fault lists. As a result, the same few characters can mean completely different things on each brand.
Mitsubishi Electric is the maker behind the familiar MSZ wall splits, such as the MSZ-AP and MSZ-EF ranges, along with ducted and cassette systems. Its codes are mostly short letter and number pairs, like P6 or U2. Mitsubishi Heavy Industries, often shortened to MHI, builds the SRK wall splits and a wide range of ducted and packaged systems. Its codes almost always start with E followed by a number, like E36 or E57.
So the first step is simple. Look at the front panel of the indoor unit, then read the compliance label on its side. Once you know the maker, you can use the right part of this page. Every code page we link below states clearly which maker the code belongs to.
Mitsubishi Electric Clues
The front badge reads Mitsubishi Electric, and wall unit model numbers often begin with MSZ. Ducted and cassette indoor units often use model prefixes such as PEA or PLA. Wired controllers typically show a two character check code.
Mitsubishi Heavy Industries Clues
The panel or label names Mitsubishi Heavy Industries. Wall splits commonly carry SRK model numbers, and many ducted systems use RC series wired controllers. Fault codes on screen begin with the letter E and a number.
How the Codes Work
How Are Mitsubishi Electric Codes Structured?
Mitsubishi Electric groups its check codes by the part of the system that raised the alarm. Once you know the pattern, a code becomes far less mysterious. In general terms, the first letter tells you roughly where to look.
P Codes
These come from the indoor unit. They cover the room and coil temperature sensors, the drain system on cassette and ducted units, coil freeze and overheat protection, and pipe temperature checks.
E Codes
These usually relate to communication. Some describe the link between indoor and outdoor units, while others describe the conversation between the remote controller and the indoor unit.
U Codes
These come from the outdoor unit. They cover discharge temperature, outdoor thermistors, compressor current and other protection functions inside the condenser.
There is one important caveat. Code lists vary between model series and generations. For example, a wall split that drains by gravity will not raise the drain pump codes that a ceiling cassette can. Therefore, always treat the code as a strong clue, then let the technician confirm it against the manual for your exact model.
The Other Mitsubishi
How Do Mitsubishi Heavy Industries Codes Differ?
MHI uses a numbered E system. Each number points to a function, and the meaning can shift a little between wall splits, packaged systems and the larger commercial ranges. For instance, E36 relates to compressor overheat on wall splits, while on packaged systems the manuals describe it as high discharge temperature.
Because of this overlap with Mitsubishi Electric letters, mix ups happen often. An MHI unit showing E6 is reporting an indoor heat exchanger sensor problem. A Mitsubishi Electric unit showing E6 is reporting a communication fault between the indoor and outdoor units. Those are very different repairs, which is exactly why the badge matters.
Similarly, E9 on an MHI system relates to drain trouble, whereas E9 on a Mitsubishi Electric system is an outdoor unit transmitting error. If you are ever unsure, take a photo of the code and the model label and send it through when you book.
Reading the Code
How Do I Retrieve a Code on My Unit?
How you see the code depends on your controller. Many homes have one of three setups, and each one reports faults a little differently.
Wired Wall Controller
Ducted systems, cassettes and some wall units use a wired controller. When a fault occurs, the screen normally shows the code, and often the unit address too. Write both down exactly as shown, including any letters.Wireless Remote Self Check
Many Mitsubishi Electric ducted and cassette systems support a self check using the wireless remote. In general terms, you press the check button to enter check mode, then the indoor unit answers with a set number of beeps and lamp blinks that match the stored code.Flashing Lamps on the Indoor Unit
Mitsubishi Electric MSZ wall splits often signal faults through the operation lamp. Count the blinks in each group, note the pause, and match the pattern to the service table. MHI SRK wall splits instead use their RUN and TIMER lights, counted in the same way.
Some wall units also have a recall mode, reached through a button combination on the remote, that reads back recent faults. That function is mainly intended for service work, so it is fine to leave it to the technician. Counting the lamp flashes is usually enough for a booking.
Lamp Patterns
What Do the Flashing Lights Mean on a Mitsubishi Electric Wall Split?
On many MSZ wall splits, the operation lamp blinks in repeating groups with a short pause between them. Service manuals for ranges such as the MSZ-AP describe patterns along these lines. Your model may differ slightly, so treat this as general guidance.
Indoor Sensor Patterns
- A single blink pattern points to the room temperature thermistor reading open or short.
- Two blinks then a pause points to the indoor coil thermistor.
- These are sensor circuit faults, not refrigerant faults.
System Patterns
- Three blinks then a pause points to no serial signal from the outdoor unit.
- Eleven blinks points to the indoor fan motor not returning a speed signal.
- Twelve blinks points to the indoor control system being unable to read its memory.
On MHI SRK wall splits, the TIMER light often stays on while the RUN light flashes a set number of times. For example, the user manuals for some SRK ranges link one RUN flash to an indoor heat exchanger sensor fault and seven flashes to insufficient refrigerant. Other patterns use the TIMER light flashing, so always check your model manual.
Code Table
What Do the Usual Mitsubishi Codes Mean?
Below is a plain language summary of the codes people ask about most often. Each one links to a full page with causes, safe checks and what a technician tests. The maker is listed on every card.
P1, Mitsubishi Electric
The indoor intake or room air temperature sensor is reading open or short circuit.
P2, Mitsubishi Electric
The indoor liquid pipe sensor, labelled TH2 in manuals, is reading out of range.
P4, Mitsubishi Electric
The drain sensor or float switch circuit is open, found on units with a drain pump.
P5, Mitsubishi Electric
Drain overflow protection has operated because water is not being pumped away.
P6, Mitsubishi Electric
The indoor coil has run too cold in cooling or too hot in heating, so protection stepped in.
P8, Mitsubishi Electric
The coil pipe temperature has not changed enough compared with the room while running.
E6, Mitsubishi Electric
The indoor unit is not receiving a valid signal from the outdoor unit.
E9, Mitsubishi Electric
The outdoor unit has detected a transmitting error on the communication link.
U2, Mitsubishi Electric
Discharge temperature leaving the compressor has gone abnormally high.
U4, Mitsubishi Electric
One of the outdoor thermistors, other than the discharge sensor, reads open or short.
E36, Mitsubishi Heavy Industries
Compressor overheat on wall splits, or high discharge temperature on packaged systems.
E57, Mitsubishi Heavy Industries
Refrigeration cycle protection, linked to low refrigerant or a closed service valve.
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Mitsubishi Electric also lists codes such as P9 for the indoor two phase pipe sensor, U3 for the outdoor discharge thermistor, UP for compressor overcurrent, and E0 to E4 for remote controller communication problems. MHI lists many more numbered codes, including E5 for indoor and outdoor communication during operation, E6 and E7 for indoor sensors, and E59 for compressor start failure on several ranges.
We have not written full pages for every code. Instead, we focused on the codes homeowners report most, and on meanings we could confirm against manufacturer documentation. If your code is not listed, note it down and call us anyway. The technician will look it up for your exact model.
Full Guides
Where Can I Read About Each Code in Detail?
Pick your code below. Each page explains the meaning in plain words, ranks likely causes from simple to serious, and lists only safe owner checks.
Mitsubishi P1
Intake air sensor fault on Mitsubishi Electric indoor units.
Mitsubishi P2
Liquid pipe thermistor fault on Mitsubishi Electric indoor coils.
Mitsubishi P4
Float switch circuit open on Mitsubishi Electric cassettes and ducted units.
Mitsubishi P5
Drain overflow protection on Mitsubishi Electric pumped drain units.
Mitsubishi P6
Coil freeze or overheat protection on Mitsubishi Electric systems.
Mitsubishi P8
Pipe temperature error on Mitsubishi Electric indoor units.
Mitsubishi E6
Indoor to outdoor signal receiving error, Mitsubishi Electric.
Mitsubishi E9
Outdoor unit transmitting error, Mitsubishi Electric.
Mitsubishi U2
High discharge temperature on Mitsubishi Electric outdoor units.
Mitsubishi U4
Outdoor thermistor open or short, Mitsubishi Electric.
Mitsubishi E36
Compressor overheat or discharge temperature, Mitsubishi Heavy Industries.
Mitsubishi E57
Refrigerant shortage or closed valve protection, Mitsubishi Heavy Industries.
Looking for another brand? The main air conditioner error codes library covers the other makes we book work for.
Before You Call
What Can I Safely Check Myself?
Plenty of faults need a technician. Still, a few basic checks are safe for any homeowner and can save a wasted visit. Stick to the list below, and stop if anything looks burnt, wet near electrics or damaged.
- Write down the code, the unit address if shown, and what the system was doing when it stopped.
- Switch the unit off at the controller, then turn off its circuit breaker for a few minutes before restoring power.
- Check the switchboard for a tripped breaker or safety switch, and reset it once only.
- Remove and wash the indoor filters if they look grey or clogged, then let them dry fully.
- Clear leaves, bins, plants and stored items from around the outdoor unit so air can move freely.
- Look at the visible end of the drain line outside to see whether it is dripping during cooling.
- Replace the remote batteries if the remote screen is faint or unresponsive.
If the code returns after these steps, leave it there. Do not open covers, touch terminals or wiring, bridge any switches, or try to add refrigerant. Those jobs belong to a licensed technician with the right gear.
Know When to Stop
When Should I Stop Using the System and Call?
Some codes clear after a power reset and never come back. That can happen after a storm, a brief outage or a one off surge. However, a code that returns within hours or days is the system telling you something is genuinely wrong.
Call Straight Away
Book promptly if you see water dripping from a ceiling cassette or ducted unit, smell burning, hear grinding from the outdoor unit, or see ice on the pipes. Switch the system off at the breaker while you wait.
Book Soon
Codes tied to sensors or communication usually stop the system rather than damage it. Even so, repeated restarts are not ideal, so book a visit rather than resetting over and over.
Monitor Briefly
A single protection code after an extreme heat day, with clean filters and a clear outdoor unit, may be worth watching. If it repeats, arrange a technician.
Getting Help
How Do I Get a Technician Out in My City?
Rapid Air Cooling is a booking service. We take your details, match the job to an independent licensed technician in your area, and dispatch them. The technicians we send hold the licences their work requires, including ARCtick licensing for any refrigerant handling. We are not a Mitsubishi dealer and do not claim manufacturer accreditation.
We book work across the five major capitals. In Sydney, start with our Sydney air conditioner repairs page or the Mitsubishi page for Sydney. Melbourne homeowners can visit air conditioner repairs Melbourne. In Queensland, see Brisbane repairs and Mitsubishi in Brisbane. Further west, there is Perth repairs and Mitsubishi in Perth, while South Australians can use Adelaide repairs and Mitsubishi in Adelaide.
You can also read our general Mitsubishi air conditioning page, browse the troubleshooting guides, or learn more about our air conditioning service Australia wide. When you call, have the code and model number handy.
Climate Matters
Why Do Some Codes Appear More in Australian Conditions?
Australia is hard on outdoor units. Long heatwaves push compressors close to their limits, so discharge temperature and coil protection codes tend to cluster in the hottest weeks of summer. A dusty or leaf choked condenser makes that worse, because it cannot shed heat properly.
Coastal homes face a different problem. Salt air slowly corrodes terminals, connectors and coil fins, which can show up later as communication or sensor faults. Meanwhile, humid summers in places like Brisbane and Sydney load the drain system heavily, so pumped drain units on cassettes and ducted systems work harder.
Storms and power interruptions matter too. A brief outage or surge can leave a controller confused, and a simple power reset often clears it. Bushfire smoke and dust also clog filters faster than many owners expect. Keeping filters clean and the outdoor unit clear is the single best way to reduce nuisance codes.
Good to Know
What Should I Know Before the Visit?
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The technician will usually start by reading the error history, because many controllers store recent codes. That history often reveals a pattern, such as a protection code that only appears on hot afternoons. So try not to clear the history yourself before the visit.
Next, they confirm the fault with testing. Sensors are measured against resistance charts, wiring is checked at both ends, and refrigerant pressures are only measured by a licensed person. Only after that do they recommend a part.
Finally, make access easy. Clear a path to the outdoor unit, and if you have a ducted or cassette system, tell us whether the roof space has a safe access hatch. Good access keeps the visit focused on the repair.
Questions
Frequently Asked Questions
Do Mitsubishi Electric and Mitsubishi Heavy Industries use the same codes?
No. They are separate manufacturers with separate code lists. Some codes look identical, such as E6 or E9, yet mean different things on each brand. Always check the badge before reading a code table.
Can I clear a Mitsubishi error code by resetting power?
Often the code clears after a power reset, but that does not fix the cause. If the code returns, the fault is still present and needs a technician to test it properly.
Why is my Mitsubishi wall unit flashing but showing no code?
Many wall splits do not have a screen, so they report faults by flashing the operation lamp. Count the blinks in each group and note the pause, then share that pattern when you book.
Is it safe to keep running a unit with a code?
Usually the system stops itself to protect its parts. Repeatedly restarting it is not recommended, especially for drain, refrigerant or compressor codes. Switch it off and book a visit.
What information should I give when I book?
Give the code or lamp pattern, the brand, the model number from the side label, the system type, and when the fault started. A photo of the controller and label helps a lot.
Does every Mitsubishi model use the same code list?
No. Lists vary by range and generation. A gravity drained wall split will not raise drain pump codes, for example. The technician confirms the meaning against your specific manual.
Can low refrigerant cause a Mitsubishi code?
Yes. On Mitsubishi Electric, codes such as U2 and P8 can be linked to refrigerant shortage. On MHI, E57 is closely tied to it. Only a licensed technician should check or add refrigerant.
Code Lookup
Look Up a Code Across Brands
The same code can mean different things on different brands. These pages compare what each code means on Daikin, Mitsubishi, Panasonic, Samsung, Fujitsu, LG and Actron.
Got a Mitsubishi Code You Cannot Clear?
Tell us the code and model, and we will book a licensed technician near you in Sydney, Melbourne, Brisbane, Perth or Adelaide.
Reviewed by AC repair and service specialist on 22 October 2026. How we write our articles