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Home > Error Codes > Mitsubishi
Every Mitsubishi ductless mini-split error code with causes and fixes. Covers M-Series, P-Series, and H2i systems.
E0
Remote Controller Signal Error
The indoor unit is not receiving signals from the remote controller. Could be a faulty remote, dead batteries, or a receiver board issue.
DIY check: Replace remote batteries. Point remote directly at the unit from close range. Check for IR interference.
E1
Indoor PCB Error
The indoor unit's printed circuit board has a fault. Internal communication failure.
DIY check: Power cycle the unit (breaker off 30 sec). If E1 returns, the indoor board needs replacement by a technician.
E2
Indoor/Outdoor Communication Error
The indoor and outdoor units cannot communicate. Wiring or connector issue between units.
DIY check: Check the communication wire between indoor and outdoor units. Look for loose connectors. Verify breaker is on for both units.
E3
Return Air Thermistor Error
The return air temperature sensor in the indoor unit has failed or is reading out of range.
DIY check: Clean the air filter (dirty filter can cause sensor misreading). If code persists, sensor replacement needed.
E4
Indoor Coil Thermistor Error
The indoor coil temperature sensor has failed. The unit cannot properly regulate cooling/heating.
DIY check: Power cycle. If persistent, the thermistor on the indoor coil needs replacement (technician).
E5
Outdoor Unit Overload
The outdoor unit is drawing too much current. Could be a compressor issue or electrical problem.
DIY check: Check that nothing is blocking the outdoor unit airflow. Clean the outdoor coil. If persistent, call a technician.
E6
Indoor/Outdoor Signal Transmission Error
Communication breakdown between indoor and outdoor units. One of the most common Mitsubishi codes. Can also indicate a drain pump or drain line issue on some models.
DIY check: Check communication wiring. Clear the condensate drain line. Power cycle both units. If persistent, a board or wiring repair is needed.
E7
Outdoor Fan Motor Error
The outdoor fan motor is not running or running at incorrect speed.
DIY check: Check if the outdoor fan is physically blocked. Listen for motor noise. Power cycle.
E8
Outdoor Unit Current Overload
Excessive current draw detected at the outdoor unit. Possible compressor or wiring issue.
DIY check: Ensure outdoor unit has adequate clearance. Clean outdoor coil. Call technician if persistent.
E9
Outdoor Communication / Compressor Temp Error
Communication error with outdoor unit or compressor discharge temperature too high. May indicate refrigerant leak or compressor failure.
DIY check: Power cycle. If E9 persists, this likely requires a technician to check refrigerant charge and compressor.
P1
Intake Sensor Error
The intake air sensor has failed or is reading abnormally.
DIY check: Clean filters. Power cycle. Sensor replacement if persistent.
P2
Indoor Pipe Temp Thermistor Error
The pipe temperature sensor on the indoor coil is faulty.
DIY check: Power cycle. Thermistor replacement needed if persistent.
P4
Drain Sensor Error
The condensate drain sensor detects an overflow or the drain pump has failed.
DIY check: Clear the condensate drain line. Check the drain pump if equipped. Water leaking from the unit is a sign.
P5
Drain Pump Error
The condensate drain pump is not operating or is blocked.
DIY check: Clean the drain pump and drain line. Check for blockages.
P6
Freezing / Overheating Protection
The evaporator coil is freezing (in cooling mode) or overheating (in heating mode). Common in dirty filter situations.
DIY check: Clean or replace the air filter (most common fix). Check that indoor airflow is not blocked by curtains or furniture. Ensure outdoor unit is clear.
P8
Pipe Temperature Abnormality / Overheat
The pipe temperature is abnormally high or the system is experiencing high-pressure protection. May indicate a refrigerant issue.
DIY check: Clean outdoor coil. Ensure outdoor unit has clearance. If persistent, refrigerant charge may be low (technician needed).
U1
Abnormal High Pressure
System pressure is too high. Could be a dirty outdoor coil, blocked airflow, or refrigerant overcharge.
DIY check: Clean outdoor coil thoroughly. Ensure unit has at least 12 inches clearance on all sides.
U2
Abnormal Low Pressure / Refrigerant
System pressure is too low. Likely indicates a refrigerant leak.
DIY check: This requires a technician with gauges to check refrigerant charge and find leaks.
U3
Outdoor DC Transmission Error
DC communication error at the outdoor unit board.
DIY check: Power cycle both units. Check wiring. Board repair if persistent.
U4
Indoor/Outdoor Transmission Error
Communication failure between indoor and outdoor units. Similar to E6 but at a different protocol level.
DIY check: Check communication wiring between units. Power cycle. May need board replacement.
U5
Abnormal Indoor/Condenser Temp
Temperature sensor reading is out of expected range.
DIY check: Clean filters and coils. Power cycle. Sensor replacement if persistent.