Mitsubishi Mini Split Error Codes Explained (2026)
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Mitsubishi error codes — quick lookup
Common Mitsubishi Electric (Mr. Slim / M-Series) mini-split codes. Codes vary by model — confirm against your unit's Mitsubishi manual. (VRF / City Multi systems use 4-digit codes.)
| Code | What it means | What to do |
|---|---|---|
E0 / E3 | Remote controller transmission error (signal not sent/received) | Re-seat remote/receiver; power-cycle |
E1 / E2 | Remote controller board fault | Power-cycle once; if it returns, call a pro |
E4 / E5 | Remote controller signal-receiving error | Check receiver line of sight/wiring; power-cycle |
E6 / E7 | Indoor ↔ outdoor communication error (often wiring) | Power-cycle; inspect interconnecting wiring; persists → tech |
E8 / E9 | Indoor/outdoor communication or transmission error | Wiring check; persists → technician |
EA / Eb / EE | Unit-count / connection / address error | Technician (wiring & addressing) |
P1 | Intake (room) air thermistor fault | Technician — sensor |
P2 / P9 | Pipe (liquid/condenser) thermistor fault | Technician — sensor |
P4 | Drain sensor / float switch connector fault | Check drain & float connector; clear clog |
P5 | Drain pump fault / drain overflow protection | Clear the clogged drain line; persists → tech |
P6 | Coil freeze-up / overheat protection | Clean filter, restore airflow |
P8 | Pipe (refrigerant line) temperature abnormal | Check airflow/filter; persists → tech (refrigerant) |
U2 | High discharge temp / overheat / refrigerant shortage | Power off — technician (refrigerant) |
U3 / U4 | Discharge thermistor open/short, or outdoor sensor fault | Technician — sensor |
U5 | Heatsink / power-module overheat | Clear outdoor-unit airflow; persists → tech |
U6 / UF | Compressor over-current / power-module fault | Power off — technician (compressor) |
Fb | Indoor unit control board fault | Technician |
Mitsubishi mini-split and heat pump systems flag a fault with a letter-and-number error code — shown by the blinking operation LED on the indoor unit, on the wireless remote’s check display, or directly on a wired controller. The first letter groups the problem: E codes are communication faults (between the remote and the unit, or between the indoor and outdoor units), P codes are protection trips (temperature sensors, the drain system, and freeze/overheat protection), and U and F codes point to the outdoor unit, compressor, and refrigerant circuit. Use the quick-answer table above to find your exact Mitsubishi error code, what it means, and the safe first step. Many E and P codes clear after a power cycle or a simple fix like cleaning the filter or clearing the drain; U-series codes usually need a licensed technician. Always confirm the code against your model’s Mitsubishi manual, since meanings vary by series (and VRF systems use 4-digit codes).
How to read a Mitsubishi error code
Where the code appears depends on your controller:
- Wall-mounted (M-Series) units: the operation indicator LED blinks a pattern, and the code shows on the wireless remote’s check display.
- Wired controllers (e.g. PAR series): the code shows directly on the screen.
What the first letter tells you
| Letter | Area of the system |
|---|---|
| E | Communication (remote ↔ unit, or indoor ↔ outdoor) |
| P | Protection: sensors, drain, freeze/overheat |
| U · F | Outdoor unit, compressor, refrigerant circuit |
What to do first
For communication (E) and many protection (P) codes, start simple:
- Turn the unit off with the remote.
- Switch off the circuit breaker for about one minute.
- Restore power and let the unit restart.
- If it’s a P4/P5 (drain) code, clear the condensate drain line; if P6/P8, clean the filter and clear anything blocking airflow.
If the same code returns, stop and have it diagnosed — repeating codes, especially U-series (compressor/refrigerant), are not DIY fixes.
Sources
- Mitsubishi Electric published error-code and service documentation (M-Series / Mr. Slim operation, installation, and service manuals; controller self-diagnosis references). Look up the exact code list for your model number on Mitsubishi Electric’s official documentation.
Trademark note: “Mitsubishi Electric” and “Mr. Slim” are trademarks of Mitsubishi Electric Corporation. This page is an independent homeowner resource and is not affiliated with, authorized by, or endorsed by Mitsubishi Electric. Brand and code references are used factually for identification and troubleshooting only.
Frequently asked questions
How do I read the error code on my Mitsubishi mini split?
On Mitsubishi Electric (Mr. Slim / M-Series) wall units, the indoor unit signals a fault by blinking the operation indicator LED, and the code can be read on the wireless remote's check display. Wired controllers (such as the PAR series) show the code directly on screen. Note the exact letters and numbers, then look them up — and confirm against your model's manual.
What does the Mitsubishi error code P8 mean?
P8 indicates a pipe (refrigerant line) temperature abnormality — the unit detected the indoor coil temperature out of its expected range. It is commonly linked to restricted airflow (a dirty filter or blocked coil), low refrigerant, or a sensor issue. Clean or replace the filter and clear anything blocking airflow; if P8 returns, have a technician check the refrigerant charge and sensors.
What is the E6 error on a Mitsubishi mini split?
E6 is an indoor-to-outdoor unit communication error. It usually points to a wiring problem on the interconnecting cable (loose, miswired, or damaged) or a control-board fault. Turn the system off at the breaker for about a minute and restore power; if E6 comes back, the wiring and boards need a technician's inspection.
Can I reset a Mitsubishi error code myself?
You can safely try one power cycle: turn the unit off at the remote, switch off its circuit breaker for about a minute, then restore power. This clears many transient faults. If the same code returns, stop — a repeating code means the underlying problem is still there and needs diagnosis.
When should I call a professional for a Mitsubishi error code?
Call a licensed HVAC technician for any compressor, refrigerant, or high-voltage code (for example U2, U6, UF) and for any code that returns after one power cycle. Refrigerant handling requires EPA Section 608 certification.