Mitsubishi Mini Split Error Code List and What it Means
When your Mitsubishi ductless mini split or heat pump suddenly breaks or starts flashing an error code, it’s not random. This is your system’s way of telling you something is wrong, and to prevent errors from becoming bigger issues. This guide lists the most common Mitsubishi error codes, what they mean, and quick things to check before calling a technician.
How to Read a Mitsubishi Mini Split Error Code
Most Mitsubishi systems — whether a mini split, City Multi, or VRF unit — use a combination of letters and numbers to flag faults.
You can find the code by:
Looking at the wall controller or remote display.
Counting the LED flashes on indoor or outdoor units.
Checking your service manual or the list below.
If the same code appears again after a reset, that’s your cue to bring in a qualified HVAC pro.
Before diving into the full list of Mitsubishi mini split error codes, it helps to understand why these systems shut down when a fault is detected. Mitsubishi units are designed with built-in safety protections that prevent damage to compressors, control boards, and electrical components.
Some error codes point to simple maintenance issues like dirty filters or blocked drain lines, while others indicate electrical or refrigerant problems that require professional service. Use the tables below as a reference guide, but avoid repeated resets if the same code keeps returning.
Mitsubishi Mini Split Error Code & Mr. Slim Error Codes
| Code | Meaning | What to Check |
|---|---|---|
| E6 | Indoor–outdoor communication fault | Power off at breaker, then ensure both units have matching wiring and tight terminal connections. |
| E9 | Transmission or signal fault | Usually wiring or board connection issue — check that communication cable isn’t damaged. |
| P1 | Room temperature sensor fault | Sensor may be unplugged or faulty; try cycling power and inspecting indoor coil sensor. |
| P4 | Drain sensor error | Drain float switch tripped — clear condensate line, then reset. |
| P5 | Drain pump failure | If the pump runs constantly or leaks, check for debris or a failed float switch. |
| P6 | Coil freeze/overheat protection | Dirty filter, blocked vents, or weak indoor fan airflow. |
| P8 | Pipe or coil thermistor fault | Thermistor open or shorted; can also indicate low refrigerant. |
| U2 | Abnormal discharge temperature | Possible low refrigerant or airflow restriction. |
| U4 | Outdoor unit communication error | Faulty control board, bad wiring, or mismatched address. |
| UP | Compressor overcurrent | Compressor locked or capacitor failing; technician required. |
If your mini split shows these codes repeatedly, shut off power for five minutes to reset.
If they reappear, contact a certified Mitsubishi service provider — persistent errors often point to control board or refrigerant issues.
Mitsubishi City Multi & VRF System Error Codes
| Code | Meaning | What to Check |
|---|---|---|
| 2502 | Drain pump fault | Drain pump stuck or blocked; check float sensor and tubing. |
| 2600 | Water leak detected | Internal leak sensor triggered — inspect drain tray. |
| 4102 | Open phase / power fault | Verify correct phase rotation and voltage supply. |
| 4220 / 4250 | Over- or under-voltage / overcurrent | Often caused by unstable power or inverter issues. |
| 5101–5103 | Thermistor faults | Sensor open/short; inspect outdoor thermistors (TH1–TH3). |
| 5701 | Float switch loose | Drain sensor unplugged or incorrectly installed. |
| 6607 | Communication line error | M-NET polarity or address conflict; check TB7 wiring. |
| 7102 | Capacity or address setting error | Usually configuration mismatch between indoor and outdoor units. |
These codes are common on City Multi and commercial VRF systems.
If you see any “4-” or “6-” series fault, turn off power and call a technician — they usually involve electrical or communication diagnostics.
Mitsubishi Electric Heat Pump & Air Conditioner Error Codes
| Code | Meaning | What to Check |
|---|---|---|
| 1102 | High discharge temperature | Dirty condenser coil or low refrigerant. |
| 1301 | Low pressure fault | Refrigerant undercharge or leak. |
| 1500 / 1501 | System overcharge or compressor shell temperature high | Too much refrigerant or blocked coil airflow. |
| E0–E3 | Controller transmission error | Reset the indoor controller; check wiring. |
| E4 | Signal receiving fault | Bad connection at remote or main PCB. |
| EE | Indoor–outdoor communication fault | Try cycling power; persistent error needs professional service. |
How to Reset or Clear Mitsubishi Error Codes
Turn the system off using the remote or wall controller.
Switch the breaker off for at least five minutes.
Restore power and turn the unit back on.
Watch for repeating error codes — if they return immediately, there’s a deeper issue.
If your system repeatedly throws the same code after a reset, don’t keep restarting it — compressors and boards can be damaged by repeated short cycling.
FAQ: Common Mitsubishi Error Questions
How do I check error codes on a Mitsubishi mini split remote?
Hold the “Check” or “Service” button until the code appears. Some models use a two-digit LED blink pattern instead.
What does Mitsubishi error code E6 mean?
It means your indoor and outdoor units aren’t communicating — often a wiring or control board issue.
Can I clear an error code myself?
You can perform a basic reset. If the same code comes back, it’s best to call for service.
Are these codes the same for every model?
Not exactly. Codes vary slightly between Mr. Slim, City Multi, and Ecodan models, but most follow the same logic.
When to Call an HVAC Technician for a Mitsubishi Mini Split Error Code
You can safely clean filters or reset power, but repeated faults like E6, P6, or 2502 signal bigger issues — refrigerant loss, failed sensors, or wiring problems.
A licensed Mitsubishi technician can:
Run diagnostic tests through service mode
Replace thermistors and control boards
Verify refrigerant charge and pressure balance
If you’re in Los Angeles or surrounding areas, reach out for Mitsubishi mini split repair or maintenance — prompt service can prevent costly compressor damage.
Final Thoughts
Mitsubishi mini split error codes are designed to protect the electrical components by shutting down when something’s wrong. Error codes are the system’s way of guiding you — a small problem now (like a clogged drain line or sensor fault) can become a major repair if ignored. Keep this list handy, and when in doubt, power down and call an expert. Please refer to the Mitsubishi Error Code Lookup for specific error codes not found in our list.
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