Troubleshooting Guide • Updated November 2026
Mitsubishi Mini Split Error Codes: Complete List & Troubleshooting Guide
Seeing an error code on a Mitsubishi mini split, Mr. Slim heat pump, or CITY MULTI controller? Look up common Mitsubishi Electric fault codes, learn what they can mean, and find safe next steps for codes such as E6, P6, 1501, 5701 and 7102.
Start here: Record the exact code and your indoor/outdoor model numbers. Code meanings can vary by equipment family.
How to Read a Mitsubishi Mini Split Error Code
The way you retrieve a fault depends on which controller and system you have. A blinking operation lamp on an M-Series wall unit is not necessarily read the same way as a four-digit fault on a CITY MULTI wall controller.
1. Indoor unit flashing lights
When the operation light blinks, count the flashes between pauses. Note which indicator is flashing, whether it alternates with another light, and the number of blinks. Some Mitsubishi Electric models use a roughly 2.5-second pause between groups, but patterns vary by model.
Do not assume “six blinks” has the same meaning across all models.
2. Handheld wireless remote
Some remotes have a small recessed CHECK button. On compatible models, with the remote turned off, aim it toward the indoor receiver and hold CHECK until the remote enters diagnosis mode. Follow your remote's manual for code retrieval and interpretation; other remotes have different procedures or no CHECK mode.
3. Wired wall controller
On compatible Mitsubishi wired controllers, a fault may appear directly on the screen. Some models provide Service → Check → Error history. Menu names and access permissions depend on controller type.
4. Outdoor unit / commercial VRF
Outdoor control boards and CITY MULTI systems may display four-digit codes, addresses, or additional detail codes. These are intended for trained technicians. Record what is visible without removing electrical panels.
If the remote displays 00 on certain Mitsubishi Electric diagnostic systems, that indicates no fault found at that moment; dashes may mean the diagnostic remote did not receive a response. Refer to the matching remote instructions.
Quick reference
Complete Mitsubishi Mini Split Error Code List
Search a code (for example, 5701, E6, P5, or 7102) or a symptom like “drain,” “thermistor,” or “communication.” The tables below group codes by equipment and fault type, with practical homeowner-safe guidance.
Showing the complete code list. Use the search box to narrow the rows.
Mitsubishi Mini Split & Mr. Slim Short Error Codes
| Code | Typical meaning | What to do |
|---|---|---|
| E0–E5 | Remote-controller communication or reception faults, depending on controller. | Check controller power/batteries if applicable. Persistent errors require controller/wiring diagnosis. |
| E6 / E7 | Indoor–outdoor serial communication error on many P-Series/Mr. Slim systems (often 6840). | Confirm external power is on; have a technician check communication wiring and boards. Details. |
| E8 / E9 | Indoor–outdoor communication receive/transmit errors on applicable models. | Record code and model; have a technician investigate wiring, supply, or electronics. |
| EE | Indoor/outdoor communication issue on certain systems. | If it returns after a single safe reset, arrange professional diagnosis. |
| P1 | Indoor return-air / intake temperature sensor (thermistor), commonly 5101. | A sensor or its connection may need testing; not fixed by filter cleaning alone. |
| P2 / P9 | Indoor refrigerant pipe temperature sensors (often 5102 / 5105). | Have a technician test sensor, connector, and wiring. |
| P4 | Drain sensor or float-switch-related fault; exact mapping varies (including 2502, 2503, or 5701). | Look for visible water; stop cooling if water is leaking. Drain detail. |
| P5 | Condensate drain-pump or overflow protection fault on applicable units. | Stop operation if water is backing up; request pump/drain inspection. |
| P6 | Freeze or overheating protection on many systems (1501 in some controller mappings). | Check washable air filters and unobstructed airflow; persistent code needs diagnosis. Details. |
| P8 | Abnormal refrigerant pipe-temperature behavior (often 1503); not simply a generic broken sensor. | Technician should check system operation, sensors, refrigerant circuit, and valves. |
| Pb | Indoor fan motor/system fault on applicable models. | Do not touch moving fan; arrange professional service. |
| Fb | Indoor controller / memory or control-system abnormality. | Controller board diagnostics may be needed. |
| U1 / Ud | High-pressure protection or overheating safeguard depending on model. | Ensure outdoor unit is not externally obstructed; professional diagnosis required. |
| U2 | High compressor discharge temperature / refrigerant-related protection (often 1102). | Stop repeat resets; a technician should investigate. Details. |
| U3 / U4 | Outdoor temperature sensor open/short faults on many P-Series systems. | Sensor and harness must be checked professionally. |
| U5 | Outdoor inverter heat-sink temperature problem. | Check unobstructed outdoor airflow visually; professional electrical diagnosis. |
| U6 | Compressor overcurrent / power-module protection. | Switch system off and arrange service; do not repeatedly restart. |
| U8 | Outdoor fan protection fault. | Visually check for external blockage without reaching into unit; service required. |
| U9 / UH | Supply voltage, power-circuit, or current-sensing abnormality. | Power/electronics diagnostics belong to a qualified technician. |
| UP / UF | Compressor overcurrent interruption / locked-compressor protection on applicable models. | Turn off system; request professional compressor/inverter diagnosis. |
Four-Digit Drain, Refrigerant & Temperature Codes
| Code | Typical meaning | What to do |
|---|---|---|
| 1102 | Compressor discharge-temperature abnormality on applicable outdoor units. | Possible refrigerant circuit, sensor, airflow, or valve issue. Details. |
| 1301 | Low-pressure abnormality on applicable CITY MULTI systems. | Requires professional refrigerant-pressure/refrigeration diagnosis. |
| 1302 | High-pressure abnormality on applicable CITY MULTI systems. | Professional pressure, airflow, and valve checks are needed. |
| 1500 | Refrigerant overcharge abnormality on certain CITY MULTI systems; other product lines may use it for a different refrigerant/superheat fault. | Check the exact model manual before interpreting. Details. |
| 1501 | Refrigerant shortage fault on certain outdoor units; freeze/overheat protection in some indoor-system mappings. | The unit and controller decide the meaning. Details. |
| 1503 | Pipe temperature fault or freeze protection depending on equipment. | Have a technician check the specific model's operating conditions. |
| 2500 | Water leakage / drain-related fault on some CITY MULTI models. | Stop use if leaking; service drainage and detection system. |
| 2502 | Drain pump or drain-sensor fault depending on series. | Check for visible water and arrange condensate diagnosis. |
| 2503 | Drain-sensor abnormality on some models. | Technician should inspect sensor and drainage system. |
| 5101 | Temperature thermistor abnormality; sensor location depends on unit. | Note whether fault belongs to indoor or outdoor unit. Details. |
| 5102 / 5103 | Temperature sensor faults; actual sensor/pipe varies by system. | Sensor resistance, connection, and harness are technician checks. |
| 5105 / 5106 | Additional refrigerant-pipe or outdoor-air temperature sensor faults on compatible systems. | Confirm specific thermistor designation in model manual. |
| 5201 / 5202 | Refrigerant pressure-sensor abnormality on applicable models. | Professional refrigerant-system and sensor testing. |
| 5701 | Loose/disconnected float-switch connector or float-switch circuit fault on many CITY MULTI / P-Series models. | Not necessarily a broken drain pump. Details. |
Electrical, Fan & Inverter Fault Codes
| Code | Typical meaning | What to do |
|---|---|---|
| 4102 | Open-phase or power-supply abnormality on certain commercial/VRF equipment. | Turn off affected system; electrical supply and control boards require technician testing. |
| 4109 | Indoor controller fault on certain units (may pair with Fb). | Technician should diagnose indoor electronics. |
| 4114 | Indoor fan trouble on applicable models. | Do not reach into unit; technician should inspect motor/feedback and controls. |
| 4115 / 4116 | Power synchronization or fan-speed issue, depending on equipment. | Requires electrical/fan-system diagnosis. |
| 4220 | DC bus-voltage abnormality / inverter power fault on applicable models. | High-voltage internal components; trained service only. |
| 4230 | Inverter heat-sink overtemperature protection on applicable models. | Outdoor fan/heat-sink and inverter diagnosis needed. |
| 4250 | Power-module/IPM overcurrent or inverter fault. | Professional compressor/inverter investigation required. |
| 4400 | Outdoor fan malfunction on applicable models. | Visually check obstruction with unit off; technician repair. |
| 5300 / 5301 | Power/current sensing or circuit abnormality depending on system. | Electrical testing by qualified professional. |
Mitsubishi CITY MULTI / M-NET Communication Codes
| Code | Typical meaning | What to do |
|---|---|---|
| 6600 | Duplicate unit / controller address on M-NET. | Installer checks network address assignments. |
| 6602 / 6603 | M-NET transmission processor / bus-busy abnormality. | Technician checks M-NET network and controllers. |
| 6606 | Transmission processor communication error. | Professional network diagnostics required. |
| 6607 | No acknowledgment (ACK) received from a network device. | Record accompanying device/address info; check by technician. |
| 6608 | No response frame / communication response abnormality. | Technician checks addressed device and transmission line. |
| 6831–6834 | MA remote-controller communication abnormalities. | Controller bus, wiring and connections need professional checks. |
| 6840 | Indoor/outdoor communication reception fault (often E6/E7 on supported systems). | Check model-specific communication wiring/service data. Details. |
| 6841–6846 | Indoor/outdoor communication, sync or wiring faults; exact code depends on model. | Technician diagnosis of communication and electrical supply. |
CITY MULTI Configuration & Connection Codes
| Code | Typical meaning | What to do |
|---|---|---|
| 7100 | Total connected capacity / unit capacity mismatch. | Installer verifies connected unit types and capacities. |
| 7101 | Capacity code or setting error. | Installer checks capacity setting against model data. |
| 7102 | Connected-unit number exceeds limit or disagrees with configured count, depending on series. | Check system setup, not refrigerant pressure. Details. |
| 7105 | Network address setting abnormality. | Installer diagnoses address configuration. |
| 7113 | Equipment configuration not settled / device identification on some CITY MULTI systems. | Installer checks configuration and addresses. |
| 7130 | Different or incompatible model detected on applicable systems. | Installer confirms compatible components and setup. |
These are selected, commonly searched Mitsubishi Electric codes—not an exhaustive service-manual index of every model, accessory, subcode, or regional product variant. A code alone does not prove which part failed.
Detailed explanations
Common Mitsubishi Fault Codes: What They Actually Mean
Several errors are frequently misidentified online. The first troubleshooting step is to match the code + model number + controller + fault location, rather than ordering a part based on a generic table.
Mitsubishi Error Code 5701: Float-Switch Connection
Typical meaning: On many Mitsubishi Electric CITY MULTI and related systems, 5701 indicates an open or disconnected float-switch circuit, sometimes described in service literature as a loose float-switch connector. It does not automatically mean the drain pump itself is faulty.
What to look for: Water around the indoor unit, a stopped system, or a recent condensate-drain issue. A technician can check the float-switch circuit and connector (called CN4F on some models), and confirm proper drainage. A few Mitsubishi product families use 5701 differently, so verify the exact model first.
Can you reset 5701? You may turn the system off, but repeated resets will not repair an open float-switch circuit. If there is water leakage, leave the system off until inspected.
Mitsubishi Error Codes 1500 and 1501: Refrigerant or Protection Faults
1500: On some CITY MULTI systems, Mitsubishi documents an overcharged refrigerant abnormality. On other systems, code 1500 is associated with abnormal superheat or low discharge-temperature behavior. The precise model matters.
1501: On some outdoor systems, 1501 means refrigerant shortage. On some indoor/controller mappings, it instead corresponds to P6 freezing or overheating protection. These descriptions should not be treated as interchangeable.
Practical next step: Note whether the fault is reported by an indoor unit or outdoor unit. Check for dirty filters or blocked airflow, but do not add refrigerant based on a code alone. An HVAC technician needs to diagnose leaks, temperature sensors, metering devices, and charge using the specified procedure.
Mitsubishi Error Code 7102: Connected Unit Count / Configuration
Typical meaning: A CITY MULTI system has detected an issue with the number of connected indoor units or their configuration. The defined limits and causes vary by model.
When it appears: Sometimes during commissioning, after replacing a control board, or after configuration changes. A technician typically checks permitted unit count, addressing, communication and connected equipment. This is not usually a homeowner maintenance issue.
What about “7102 51”? The trailing number may be a unit address or detail field on the controller, rather than an entirely different fault code. Save a photo of the full screen and consult the specific controller manual.
Mitsubishi Error Code 1102 / U2: Compressor Discharge Temperature
Typical meaning: A discharge-temperature abnormality. Possible causes include refrigerant shortage, temperature-sensor problems, restricted refrigerant flow, or valve issues, depending on model and operating conditions.
What to do: Visually check that the outdoor unit can breathe, then stop using the system if the code persists. Avoid repeated power cycles; these faults require professional diagnosis.
Mitsubishi Error Code 5101: Temperature Sensor / Thermistor
Typical meaning: A thermistor fault. On many indoor P-Series units, 5101 corresponds to the intake-air sensor (P1); on other Mitsubishi systems, 5101 may identify a different temperature sensor, such as an outdoor discharge or air-inlet thermistor.
What to do: Record which unit reports the code, then have the sensor and wiring checked using the corresponding service manual. It is not safe to assume a universal sensor location.
Mitsubishi E6 / E7 / E9 / 6840: Indoor–Outdoor Communication
Typical meaning: The indoor and outdoor units are not communicating normally. A service technician may investigate communication wiring, terminals, power, or circuit boards. E7 and E9 should not be interpreted as universal fan-motor codes; manufacturer definitions depend on system series.
What to do: Confirm the normal house breaker is on and take a picture of the controller. Do not open service panels or touch S1/S2/S3 terminals: those connections can carry dangerous voltage even when described as “communication wiring.”
Mitsubishi P6: Coil Freeze / Overheat Protection
Typical meaning: The system is protecting itself from an abnormal heat-exchanger temperature condition. Restricted airflow is one possible contributor, but refrigerant issues, fan problems, and sensors may also be involved.
What to do: With the system off, clean accessible filters according to the manufacturer's directions, reopen blocked indoor airflow paths, and look for visible icing. If the code returns, stop resetting and arrange a professional inspection.
Mitsubishi Mini Split Blinking Lights: 6, 7, 11 or 14 Flashes
Some Mitsubishi Electric wall units report failures through operation-indicator flash patterns rather than displaying a text code. For certain Mitsubishi Electric room-air-conditioner models, published guidance includes these examples:
| Light pattern | Possible fault on applicable models | Next step |
|---|---|---|
| 6 flashes | Outdoor inverter/startup or overcurrent protection. | Stop repeat starts; service technician. |
| 7 flashes | Outdoor control system / thermistor or board problem (model-specific). | Record complete pattern and model. |
| 11 flashes | Indoor fan-motor feedback abnormality. | Stop unit; professional fan diagnosis. |
| 14 flashes | Refrigerant-circuit or outdoor operating abnormality on some models. | Professional refrigerant-system diagnosis. |
Do not use this table without matching the model. Different products may use different lamps, flash groups, or timing. Count flashes between complete pauses and check the model's operation manual. See Mitsubishi Electric's official blinking-light guide for example patterns on supported units.
How to Reset or Clear Mitsubishi Mini Split Error Codes
A reset may clear a temporary fault, but it cannot repair failed components, refrigerant leaks, unsafe wiring, or an active drainage issue. Save the code first so you do not erase useful diagnostic history.
- Record the fault. Photograph the code, any flashing lights, and the indoor model-number sticker if safely accessible.
- Turn the system off with its normal controller. Wait for fans to stop.
- Check basic, accessible items: air filter, closed indoor airflow path, and obvious outdoor obstructions. Never open an electrical cabinet or refrigerant connection.
- If the manual permits a power reset, turn the unit off at its properly identified circuit breaker or disconnect, wait the interval stated in the model's instructions (commonly several minutes), then restore power once.
- If the code returns, stop. Repeated resets can obscure a persistent fault and may contribute to equipment damage.
What You Can Check Yourself—and What Needs a Technician
Homeowner-safe checks
- Write down the complete fault code and model numbers.
- Clean accessible, washable filters as directed in the manual.
- Keep furniture and curtains clear of indoor air intakes.
- Look for leaves or visible debris around the outdoor unit, without opening it.
- Check whether water is visibly leaking or ice is forming.
- Perform one manufacturer-permitted reset if appropriate.
Technician-only diagnostics
- Testing electrical supply, communication terminals and circuit boards.
- Opening indoor/outdoor equipment covers.
- Testing thermistor resistance, inverter power modules and compressors.
- Opening or servicing refrigerant lines, checking charge, and repairing leaks.
- Servicing float-switch wiring, drain pumps and inaccessible electrical components.
- Reconfiguring CITY MULTI addresses or connected unit capacities.
One important diagnostic distinction: the fault code identifies what the system detected, not necessarily the failed part. A P6 protection fault, for example, can have more than one cause, and an E6 communication fault does not prove that the control board needs replacement. Matching operating conditions, model-specific tests and the exact fault history prevents guesswork.
Mitsubishi Error Code FAQs
How do I check Mitsubishi mini split error codes on the remote?
On some handheld Mitsubishi Electric remotes, turn the remote off, point it at the indoor unit, and hold the recessed CHECK button to enter diagnosis mode. Other remotes use a different button sequence, and some don't offer code lookup. Check the remote and indoor-unit manuals before trying. Wired controllers may offer an error history through a Service/Check menu.
What does Mitsubishi error code E6 mean?
On many Mitsubishi Electric P-Series/Mr. Slim systems, E6 indicates a problem receiving communication between the indoor and outdoor units, sometimes represented by four-digit code 6840. A trained technician may check power, communication circuits, wiring and boards.
What is Mitsubishi error code FH?
“FH” is not a universal Mitsubishi Electric mini split fault across all product families. It may be a display/status indication or a code from a different manufacturer/series. Verify the exact brand (Mitsubishi Electric versus Mitsubishi Heavy Industries), model number, controller and whether the screen shows FH or a similar-looking code before assigning a meaning.
What does Mitsubishi error code 5558 mean?
5558 is not identifiable as a universal residential Mitsubishi Electric error code from the broadly applicable tables used here. Record the complete equipment model and any accompanying detail code; confirm through the specific service manual or manufacturer's technical support rather than relying on a generic interpretation.
Are Mitsubishi Electric and Mitsubishi Heavy Industries error codes the same?
No. They are separate manufacturers with different equipment families and service literature. A fault code that applies to one should not be assumed to mean the same thing on the other.
Why is my Mitsubishi mini split blinking but still working?
Some lights indicate normal operation, warm-up, defrost, or mode conflicts; others indicate recorded or active faults. The specific model's light pattern and operating manual determine which it is. A repeating error or loss of heating/cooling warrants diagnosis.
Is “00” a Mitsubishi error code?
On certain Mitsubishi Electric remote-controller diagnostic systems, 00 indicates no detected error at the time of the check. It does not guarantee every component is healthy, and behavior varies by controller.
Can I reset a Mitsubishi error code by turning off the breaker?
A single power reset may be allowed by the manufacturer's instructions, but only after recording the fault and ensuring there is no active electrical, refrigerant, water-leak, or mechanical hazard. If the fault comes back, stop and have the system inspected.
Where do I find the Mitsubishi mini split model number?
Look for the manufacturer's identification label on the indoor unit and outdoor condenser, in the owner's manual, or on installation paperwork. Model numbers commonly start with prefixes such as MSZ, MUZ, PKA, PEAD, PUZ or other series-specific identifiers. Record both indoor and outdoor models whenever possible.
Should I replace my mini split because of an error code?
Not automatically. Many codes indicate serviceable issues. Replacement may be worth comparing with repair when equipment is older, problems repeat, key parts are unavailable, or repair costs are unusually high. The decision should follow an actual diagnosis, not the error code alone.
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Explore Mini Split InstallationGet an Online Installation QuoteManufacturer References & Important Notes
The code descriptions above are cross-checked against manufacturer resources, but they are not a substitute for your exact model's service manual. Product generations, markets and controllers may use different mappings.
- Mitsubishi Electric – Official Error Code Lookup
- Mitsubishi Electric – Operation Lamp & Remote Code Troubleshooting
- Mitsubishi Electric – PAA Service Manual, Check Code Table (PDF)
- Mitsubishi Electric – Technical Fault Code Reference (PDF)
Content reviewed November 10, 2026. General information only. Maximum Comfort Heating & Air Conditioning is an independent HVAC contractor and this guide is not an official Mitsubishi Electric publication. For a code that is missing or unclear, consult the manual for the indoor/outdoor model combination.