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Error code reference

LG Microwave Error Code E-42

Easy/PH sensor short error

LG codesLG microwave codes

Easy/PH sensor short error - sensor terminals shorted.

First step from the service manual

Check if both terminals of the sensor are slightly shorted.

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

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  • Step-by-step tests with expected resistance, voltage, and continuity values
  • Wiring diagram references and connector pinouts from the OEM service manual
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What E-42 means on a LG microwave

The E-42 error code on an LG microwave indicates an Easy Clean or PH sensor short fault. This error is triggered when the control board detects that the two terminals of the humidity or sensor circuit are shorted together, creating an abnormally low resistance path where there should be measurable resistance. The sensor in question is used by the microwave to detect steam or humidity levels inside the cavity, which allows automatic cooking functions to determine when food is properly heated. When the control board reads a shorted condition across these terminals, it halts operation to prevent incorrect cooking behavior or component damage.

The most direct diagnostic starting point is measuring the resistance across both terminals of the sensor itself. A properly functioning sensor will show a defined resistance range, while a shorted sensor will read near zero ohms. The short can occur within the sensor body itself due to internal component failure, or it can result from moisture or debris bridging the two terminals externally. Wiring harness damage, including pinched or melted insulation causing two conductors to contact each other, can also produce the same shorted reading at the control board.

Because this fault involves the sensor circuit rather than the magnetron or high-voltage system directly, the diagnostic process is relatively contained. Technicians should isolate the sensor from the wiring harness before measuring resistance to determine whether the fault is in the sensor itself or in the connecting wiring. If the sensor reads normal resistance when disconnected, the harness or control board connector should be inspected for damage, corrosion, or contamination that could be causing the short condition.

Source: manufacturer service documentation.

Common causes of E-42

  1. 01

    Failed humidity or PH sensor

    Part replacement

    The sensor itself can fail internally, causing its two terminals to short together. Disconnecting the sensor and measuring resistance across its terminals will confirm this if the reading is near zero ohms.

  2. 02

    Moisture or condensation on sensor terminals

    Wiring / connection

    Excess moisture inside the microwave cavity can bridge the sensor terminals and create a false short reading. Inspect the sensor area for visible water, grease buildup, or food residue contacting both terminals.

  3. 03

    Damaged wiring harness

    Part replacement

    Pinched, melted, or frayed wiring between the sensor and the control board can cause two conductors to contact each other, producing a shorted signal at the board. Inspect the harness routing for any physical damage or burned insulation.

  4. 04

    Corroded or contaminated connector

    Wiring / connection

    Corrosion or food grease inside the sensor connector plug can create conductive bridging between the two terminal pins. Visually inspect the connector and clean or replace it if contamination is present.

  5. 05

    Faulty control board

    Part replacement

    If the sensor and all wiring test correctly, the control board itself may be misreading the sensor circuit due to a failed input component on the board. This is the least common cause and should be diagnosed after ruling out all other possibilities.

See the test procedure for each cause

Frequently asked questions about E-42

What does E-42 mean on a LG microwave?
E-42 on an LG microwave indicates an Easy Clean or PH sensor short error, meaning the control board has detected that both terminals of the humidity sensor are shorted together. This prevents normal operation because the microwave cannot read accurate sensor data. The fault points to the sensor itself, the connecting wiring, or the terminal connector.
Can I fix the E-42 error myself on an LG microwave?
Some causes of E-42 are accessible to a knowledgeable DIYer, such as cleaning contamination off sensor terminals or inspecting the wiring harness for visible damage. However, replacing the sensor or control board requires disassembling the microwave, and the high-voltage capacitor inside can retain a dangerous charge even when unplugged. If you are not experienced with appliance electronics, professional service is strongly recommended.
Is it safe to use my LG microwave while it shows E-42?
No, the microwave will typically not operate while displaying E-42 because the fault prevents normal sensor readings. Attempting to bypass or ignore the error is not advisable, as the sensor is part of the cooking control system. The unit should remain out of service until the short condition is diagnosed and corrected.
Will resetting my LG microwave clear the E-42 error?
Unplugging the microwave for a few minutes and restoring power may temporarily clear the error display, but the code will return if the underlying short condition in the sensor circuit still exists. A reset does not repair the shorted terminals or any wiring fault. A proper repair requires physically inspecting and correcting the sensor or wiring problem.
How much does it cost to repair an LG microwave with an E-42 error?
Repair costs vary depending on the root cause. Sensor replacement parts typically range from $15 to $60, while a new control board can range from $80 to $200 or more depending on the model. Adding professional labor, total repair costs can range from $100 to $300. In some cases, if the microwave is older or the cost approaches the price of a new unit, replacement may be more economical.

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