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Error code reference

Midea Air Conditioner Error Code E4

Communication malfunction between main control board and display board (no feedback received within 120…

Midea codesMidea air conditioner codes

Communication malfunction between main control board and display board (no feedback received within 120 seconds).

First step from the service manual

Check signal wire between the display board and main board for proper connection.

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

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What E4 means on a Midea air conditioner

The E4 error code on a Midea air conditioner indicates a communication malfunction between the main control board and the display board. Specifically, the main control board has not received any feedback signal from the display board within a 120-second window. This timeout-based fault detection is built into the system to identify when the two boards have lost the ability to exchange data, which is necessary for normal operation including user input processing, mode selection, and status reporting.

The communication between the main board and display board typically occurs over a dedicated signal wire or data bus. When this connection is interrupted, degraded, or completely absent, the main board registers the communication timeout and triggers the E4 code. Common physical causes include a loose or disconnected signal wire connector at either board, a pinched or broken wire within the harness, or corrosion on the connector pins that increases resistance and disrupts signal integrity.

In some cases, the fault lies not in the wiring but in the boards themselves. A failed display board that is no longer transmitting feedback, or a main control board with a damaged communication circuit, can produce the same 120-second timeout condition. Power supply issues affecting one board but not the other can also cause this error, since both boards need stable voltage to maintain communication. Beginning diagnosis at the signal wire connection, as recommended, helps rule out simple wiring faults before condemning either board.

Source: manufacturer service documentation.

Common causes of E4

  1. 01

    Loose or disconnected signal wire

    Wiring / connection

    The signal wire connecting the display board to the main control board may have come loose at either connector. Inspect both ends of the harness for proper seating and push connectors firmly into place.

  2. 02

    Damaged or broken signal wire

    Part replacement

    The wire itself may be pinched, cut, or broken internally, especially if the unit has been serviced recently or if the wire routes near a moving component. Visually trace the full length of the harness and check for continuity with a multimeter.

  3. 03

    Corroded connector pins

    Wiring / connection

    Moisture intrusion can cause oxidation on the connector pins, increasing resistance and disrupting the communication signal. Look for green or white residue on the pins and clean with electrical contact cleaner if found.

  4. 04

    Failed display board

    Part replacement

    If the display board has failed internally, it will not transmit the feedback signal the main board expects, triggering the 120-second timeout. A board failure is suspected when wiring checks out but the error persists.

  5. 05

    Failed main control board

    Part replacement

    A damaged communication circuit on the main control board can prevent it from receiving signals even when the display board and wiring are functioning correctly. This is typically the last component to suspect after other causes are eliminated.

See the test procedure for each cause

Frequently asked questions about E4

What does E4 mean on a Midea air conditioner?
The E4 code means the main control board did not receive any communication feedback from the display board within 120 seconds. This communication timeout causes the unit to stop normal operation and display the fault code. The error points to a problem in the signal wiring between the two boards or a failure of one of the boards itself.
Can I fix the E4 error myself?
In many cases, yes. Start by powering off the unit and inspecting the signal wire harness between the display board and main control board for loose, disconnected, or visibly damaged connectors. Reseating the connectors and restarting the unit resolves the issue when a simple connection problem is the cause. If the wiring checks out and the error returns, board replacement is likely needed and may require a technician.
Will resetting the unit clear the E4 error?
A power reset may temporarily clear the error, but if the underlying communication fault is still present, the E4 code will return within 120 seconds of the unit restarting. A reset is useful for confirming whether the fault is intermittent or persistent, but it does not fix the root cause. The signal wiring and boards should be inspected before assuming a reset has resolved the problem.
Is it safe to run my Midea air conditioner with an E4 error?
The unit will generally not operate normally while the E4 fault is active, as the communication failure prevents reliable control of the system. Attempting to bypass or ignore the fault is not recommended. Address the underlying wiring or board issue before returning the unit to service to avoid further component damage.
How much does it cost to repair an E4 error on a Midea air conditioner?
If the fix is simply reseating a loose connector, there is no parts cost and only minimal labor time involved. If the signal wire harness needs replacement, parts and labor costs are typically in the range of $50 to $150. Replacing a display board or main control board generally costs between $100 and $350 depending on the specific model and labor rates in your area.

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