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Error code reference

LG Microwave Error Code E-81

CB (control board) communication error.

LG codesLG microwave codes

CB (control board) communication error.

First step from the service manual

Check main harness and display connector.

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

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  • Wiring diagram references and connector pinouts from the OEM service manual
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What E-81 means on a LG microwave

The E-81 error code on an LG microwave indicates a communication failure between the main control board (CB) and the display board. These two boards exchange data continuously through a dedicated wiring harness, and when that communication link is interrupted or degraded, the microwave halts operation and throws this fault code. The error points specifically to the internal communication bus rather than a power supply failure or a sensor fault.

The most common entry point for diagnosis is the main harness and the display board connector, as LG specifies in its first diagnostic step. Loose, corroded, or damaged connector pins are a frequent cause of intermittent or complete communication loss. Vibration over time, moisture exposure, or a connector that was not fully seated during a previous repair can all break the data path between the two boards. Visually inspecting the harness for pinched wires, burn marks, or corrosion at the connector terminals is the correct starting point.

If the harness and connectors check out and the error persists, one of the two control boards is likely at fault. Either the main control board has failed internally and is no longer transmitting data correctly, or the display board has lost its ability to receive and respond to those signals. Replacing components without fully ruling out wiring issues first is not recommended, as board replacements are significantly more costly than harness repairs.

Source: manufacturer service documentation.

Common causes of E-81

  1. 01

    Loose or disconnected display connector

    Wiring / connection

    The connector between the main harness and the display board may have worked loose over time. Check that the connector is fully seated and that no pins are bent or pushed back.

  2. 02

    Damaged or pinched main harness

    Part replacement

    The wiring harness running between the main control board and the display board can be pinched, cut, or worn through, breaking the communication circuit. Inspect the full length of the harness for visible damage.

  3. 03

    Corroded connector terminals

    Wiring / connection

    Moisture inside the microwave cavity can cause oxidation on the harness connector pins, increasing resistance and disrupting the data signal. Look for green or white residue on the terminals and clean or replace the connector as needed.

  4. 04

    Failed display board

    Part replacement

    If the harness and connectors are intact, the display board itself may have failed and is no longer able to communicate with the main control board. This typically requires board replacement.

  5. 05

    Failed main control board

    Part replacement

    The main control board may have suffered an internal failure that prevents it from sending communication signals to the display board. This is the least likely cause but should be evaluated after ruling out all wiring and connector issues.

See the test procedure for each cause

Frequently asked questions about E-81

What does E-81 mean on a LG microwave?
E-81 is a control board communication error, meaning the main control board and the display board have lost contact with each other through the internal wiring harness. The microwave cannot operate when this communication link is broken. Diagnosis should start with inspecting the main harness and the display board connector for loose, corroded, or damaged connections.
Can I fix the E-81 error myself?
In many cases, yes. Start by unplugging the microwave and inspecting the connector between the main harness and the display board. If the connector is loose, re-seating it may resolve the error. If the harness is visibly damaged or the terminals are corroded, a more involved repair is needed. Control board replacement requires comfort working with electronics and is better left to a technician if you are unsure.
Will resetting the microwave clear the E-81 error?
A power reset by unplugging the microwave for one to two minutes may temporarily clear the code if the communication failure was caused by a transient glitch. However, if the underlying cause is a loose connector, damaged harness, or faulty board, the error will return. A reset alone is not a repair and should be followed by a proper inspection.
Is it safe to use my LG microwave while the E-81 error is displayed?
No. The E-81 error indicates the control boards cannot communicate, which means the microwave will not operate normally and may not respond to commands correctly. You should not attempt to use the appliance until the fault has been diagnosed and repaired.
How much does it cost to repair an E-81 error on an LG microwave?
Repair costs vary depending on the root cause. If the fix is simply re-seating a connector, there may be no parts cost and minimal labor. Harness replacement typically runs in the range of $20 to $80 for parts. A display board or main control board replacement can cost anywhere from $60 to $200 or more for the part alone, plus labor if a technician performs the work.

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