Mitsubishi Air Conditioner Error Code E.MP

E.MP means the inverter drive could not determine the magnetic pole position of the motor during offline auto tuning because the rotation command differed from the actual detected motor rotation direction. This is most often caused by mis-wired encoder cables or an incorrect Pr.359 parameter setting. The system generates this fault to prevent damage from uncontrolled motor operation. A technician must inspect the wiring and configuration before the unit can operate normally.

No. The E.MP fault locks out motor operation because the inverter cannot safely control the motor without a confirmed magnetic pole position. Attempting to force the unit to run in this condition could damage the motor, the inverter drive, or both. The system should remain off until the fault is diagnosed and resolved.

If the fix is simply correcting the Pr.359 parameter or reseating the encoder cable, the cost is primarily the technician's labor, which typically ranges from around 75 to 200 dollars depending on your location and the service provider. If the encoder sensor itself needs to be replaced, parts and labor combined can range from 150 to 500 dollars or more. A motor replacement represents the higher end of repair costs and can range from several hundred to over a thousand dollars depending on the unit.

If you are comfortable working with inverter drive parameters and low-voltage signal wiring, you can check the Pr.359 setting and visually inspect the encoder cable connections for obvious mis-wiring. However, correcting parameter settings incorrectly or working near live inverter components carries a risk of equipment damage or injury, so most homeowners should contact a qualified technician. Diagnosing a damaged encoder or motor winding fault also requires specialized test equipment.

Resetting the unit will clear the displayed fault code temporarily, but the error will return immediately when the inverter attempts offline auto tuning again if the underlying cause has not been corrected. The mis-wiring or incorrect parameter that triggered the fault must be addressed first. A reset alone is not a repair.