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Error code reference

LG Microwave Error Code E-27

Initial temperature error at MW mode

LG codesLG microwave codes

Initial temperature error at MW mode - abnormal temperature sensed when oven is in MW mode.

First step from the service manual

Press the Cancel key to cancel the current state; check sensor connectivity.

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

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What E-27 means on a LG microwave

The E-27 error code on an LG microwave indicates an initial temperature error detected during microwave (MW) mode operation. Specifically, the control system has read an abnormal temperature from the cavity temperature sensor at the moment MW mode is initiated or during its operation. This sensor monitors internal oven temperature and feeds readings back to the main control board. When those readings fall outside the expected range at startup or during MW operation, the control board triggers E-27 to prevent the unit from running under potentially unsafe or inaccurate thermal conditions.

The temperature sensor involved is typically a thermistor or thermocouple mounted inside the microwave cavity. A faulty sensor can report values that are either too high or too low for what the control board considers acceptable for normal MW mode operation. The wiring harness connecting the sensor to the control board is equally important: loose connectors, pinched wires, or corroded terminals can produce erratic resistance readings that the board interprets as an abnormal temperature condition.

The first recommended diagnostic step is to press the Cancel key to clear the current state, then inspect all sensor wiring connections for security and damage. If the error returns after clearing, the sensor itself or the wiring harness will need to be tested for proper resistance output. The main control board should only be considered as a replacement candidate after the sensor and its wiring have been ruled out as the source of the fault.

Source: manufacturer service documentation.

Common causes of E-27

  1. 01

    Loose or disconnected sensor wiring

    Wiring / connection

    The wiring harness connecting the cavity temperature sensor to the control board may have a loose connector or a terminal that has worked free over time. Check all connector plugs at both the sensor end and the board end for secure seating.

  2. 02

    Faulty cavity temperature sensor

    Part replacement

    The temperature sensor (thermistor or thermocouple) inside the microwave cavity may have failed and is reporting out-of-range resistance values. A failed sensor will need to be replaced to restore accurate temperature feedback.

  3. 03

    Corroded or damaged sensor connector terminals

    Wiring / connection

    Moisture or heat exposure can corrode the metal terminals inside the sensor wiring connectors, increasing resistance in the circuit and causing erratic readings. Inspect terminals visually and clean or replace connectors as needed.

  4. 04

    Damaged sensor wiring harness

    Part replacement

    The wire leading from the temperature sensor to the control board may be pinched, burned, or broken, interrupting the signal. Trace the full length of the harness and look for visible damage or continuity breaks.

  5. 05

    Defective main control board

    Part replacement

    If the sensor and all associated wiring test within normal parameters, the main control board may be misreading the sensor signal due to internal component failure. The board should only be considered for replacement after all other causes are eliminated.

See the test procedure for each cause

Frequently asked questions about E-27

What does E-27 mean on a LG microwave?
E-27 on an LG microwave indicates an initial temperature error in microwave (MW) mode, meaning the control board detected an abnormal temperature reading from the cavity sensor when the oven was operating. The unit shuts down to prevent running under inaccurate thermal conditions. The fault points to the temperature sensor, its wiring, or in rarer cases the main control board.
Can I fix E-27 myself without calling a technician?
The first step anyone can take is pressing the Cancel key to clear the error and then restarting the microwave. If the error returns, you can inspect the sensor wiring connectors for looseness or corrosion without any special tools. However, testing the sensor for correct resistance output and working inside the cabinet near the high-voltage capacitor requires caution and some technical experience, so less confident DIYers should consider professional service.
Is it safe to use my LG microwave while it shows E-27?
No, you should not continue operating the microwave while E-27 is active. The error means the control system cannot confirm accurate temperature conditions inside the oven cavity during MW mode. Running the unit without reliable temperature monitoring could allow it to overheat, which presents a safety risk. Stop using it until the fault is diagnosed and resolved.
Will resetting the microwave clear the E-27 error?
Pressing the Cancel key is the recommended first step and may temporarily clear the code. However, if the underlying cause is a faulty sensor or damaged wiring, the error will return the next time MW mode is used. A reset alone is not a repair, only a way to confirm whether the fault is intermittent or persistent.
How much does it cost to repair an E-27 error on an LG microwave?
Repair costs vary depending on the faulty component. A replacement cavity temperature sensor is generally an inexpensive part, typically in the range of $10 to $40 for the part alone, while professional labor to diagnose and install it could bring the total to $80 to $150 or more. If the main control board is at fault, parts alone can range from $50 to $200 or higher, making professional repair costs comparable to replacement for older units.

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