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Error code reference

Mitsubishi Air Conditioner Error Code E.EP

Encoder phase fault

Mitsubishi codesMitsubishi air conditioner codes

Encoder phase fault - rotation command differs from actual motor rotation direction detected from encoder during offline auto tuning.

First step from the service manual

Check for mis-wiring of encoder cable and Pr.359/Pr.852 setting.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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What E.EP means on a Mitsubishi air conditioner

The E.EP error code on a Mitsubishi air conditioner indicates an encoder phase fault detected during offline auto tuning. Specifically, the drive has determined that the rotation command it issued to the motor does not match the actual rotation direction being reported back by the encoder. This mismatch is caught during the auto tuning sequence, which is a pre-operational calibration process the drive uses to characterize motor behavior before normal operation begins. The encoder provides real-time shaft position and direction feedback to the inverter drive, and any discrepancy between commanded and detected rotation direction triggers this fault.

The most common source of this fault is incorrect wiring of the encoder cable. If the encoder signal wires are swapped or connected to the wrong terminals, the drive will receive phase feedback that is reversed relative to its command, causing the fault to trip immediately during tuning. Parameter settings Pr.359 and Pr.852 are also directly involved, as these parameters govern encoder-related control behavior and motor rotation direction configuration within the drive. An incorrect value in either parameter can create a logical mismatch even when the physical wiring is correct.

Resolving E.EP requires a systematic check of both the encoder cable wiring and the relevant parameter configuration. Technicians should verify that each encoder wire is landed on the correct terminal per the drive wiring diagram, checking for swapped A-phase and B-phase signal leads in particular. After confirming wiring integrity, Pr.359 and Pr.852 should be reviewed and corrected to values appropriate for the connected motor and encoder type before retrying the auto tuning sequence.

Source: manufacturer service documentation.

Common causes of E.EP

  1. 01

    Swapped encoder cable wiring

    Wiring / connection

    If the A-phase and B-phase signal leads on the encoder cable are reversed at the terminal block, the drive receives direction feedback that is opposite to its command. Visually inspect the encoder cable connections against the wiring diagram and verify each wire is landed on the correct terminal.

  2. 02

    Incorrect Pr.359 or Pr.852 parameter setting

    Wiring / connection

    Parameters Pr.359 and Pr.852 control encoder feedback behavior and rotation direction logic within the drive. If either parameter is set to a value incompatible with the connected motor or encoder, the fault will trigger during auto tuning even if physical wiring is correct.

  3. 03

    Damaged or partially failed encoder cable

    Part replacement

    A damaged encoder cable with broken conductors or poor connector seating can cause intermittent or corrupted phase signals, leading the drive to detect a direction mismatch. Inspect the cable along its full length for pinching, cuts, or loose connector seating.

  4. 04

    Faulty encoder unit

    Part replacement

    If the encoder itself has failed internally, it may output incorrect or reversed phase signals regardless of correct wiring. This is less common than wiring issues but should be considered after wiring and parameters have been confirmed correct.

  5. 05

    Incompatible motor or encoder type for the configured parameters

    Wiring / connection

    Using a motor or encoder that does not match the type expected by the current drive parameter configuration can produce a phase direction fault during tuning. Confirm that the motor and encoder specifications match what is set in the drive parameters.

See the test procedure for each cause

Frequently asked questions about E.EP

What does E.EP mean on a Mitsubishi air_conditioner?
E.EP is an encoder phase fault that occurs during offline auto tuning. The drive detects that the actual rotation direction of the motor, as reported by the encoder, does not match the rotation command it sent. This fault prevents the system from completing its tuning sequence and entering normal operation. It is most often caused by incorrect encoder cable wiring or an improper setting in parameters Pr.359 or Pr.852.
How do I fix the E.EP error on a Mitsubishi air conditioner?
Start by inspecting the encoder cable wiring and confirming each signal lead is connected to the correct terminal, paying close attention to the A-phase and B-phase leads. Next, review and correct parameters Pr.359 and Pr.852 to ensure they match the motor and encoder being used. Once wiring and parameters are confirmed correct, clear the fault and retry the auto tuning sequence. If the fault persists after those steps, inspect the encoder cable for damage or test the encoder itself.
Is it safe to keep running my air conditioner with the E.EP error?
No. The E.EP fault halts the auto tuning process and prevents the drive from operating the motor correctly. Attempting to force operation with this fault active could result in improper motor control and potential damage to the drive or motor. The fault must be diagnosed and resolved before the system is returned to service.
Will resetting the unit clear the E.EP error?
A reset will clear the active fault indication, but the fault will return the next time auto tuning is initiated if the underlying cause has not been corrected. Simply resetting without addressing the encoder wiring or parameter settings will not resolve the problem. The root cause must be identified and fixed before the tuning sequence can complete successfully.
How much does it cost to repair the E.EP fault on a Mitsubishi air conditioner?
If the fault is caused by a wiring error or incorrect parameter settings, repair costs are typically limited to labor time for diagnosis and correction, often in the range of $75 to $200 depending on the technician and location. If the encoder cable or encoder unit requires replacement, parts costs can add $50 to $300 or more to the total, depending on the specific components involved. Getting a diagnostic assessment from a qualified technician is the best way to estimate the total cost for your specific situation.

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