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Error code reference

LG Refrigerator Error Code Error4

Defrost sensor abnormal

LG codesLG refrigerator codes

Defrost sensor abnormal - short circuit or open circuit.

First step from the service manual

Check resistance at both ends of the defrost sensor at CON7 PIN 3,4.

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

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What Error4 means on a LG refrigerator

Error4 on an LG refrigerator indicates an abnormal condition in the defrost sensor circuit. Specifically, the control board has detected either a short circuit or an open circuit in the defrost sensor, which is a thermistor responsible for monitoring the temperature of the evaporator during the defrost cycle. This sensor feeds real-time temperature data to the main control board so the system knows when to terminate the defrost heater cycle. When the circuit reads outside the expected resistance range, the board flags Error4 and may suspend or alter normal defrost operation.

The first diagnostic step is to measure resistance at both ends of the defrost sensor at CON7, PIN 3 and PIN 4 on the control board connector. A properly functioning defrost thermistor will read a specific resistance value that corresponds to the current temperature at the evaporator. An open circuit reading (infinite or no continuity) indicates a broken wire or a failed thermistor that has lost internal contact. A short circuit reading (near-zero resistance) points to a shorted thermistor element or a wiring harness fault where the two conductors are making unintended contact.

Common root causes include physical damage to the sensor wiring harness from ice buildup in the freezer compartment, a thermistor that has degraded over time and drifted out of specification, or a corroded connector at CON7. It is also worth inspecting the wiring path between the sensor and the connector for pinching, burn marks, or moisture intrusion. Resolving this error requires confirming the wiring integrity before condemning the sensor itself.

Source: manufacturer service documentation.

Common causes of Error4

  1. 01

    Failed defrost sensor (thermistor)

    Part replacement

    The thermistor element inside the defrost sensor can degrade or fail outright, producing an open or short circuit reading at CON7 PIN 3 and PIN 4. This is the most frequent cause and is confirmed by measuring resistance directly at the sensor leads.

  2. 02

    Damaged wiring harness

    Part replacement

    Ice accumulation in the freezer compartment can press against the sensor wiring and eventually crack insulation or sever conductors, causing an open circuit. Inspect the full wiring path from the evaporator area to the CON7 connector for visible damage.

  3. 03

    Corroded or loose connector at CON7

    Wiring / connection

    Moisture exposure can corrode the pins at CON7, increasing resistance or breaking continuity entirely. Unplug the connector and inspect PIN 3 and PIN 4 for rust, debris, or bent pins that would cause an intermittent or failed reading.

  4. 04

    Pinched or shorted wiring

    Part replacement

    If two conductors in the harness contact each other due to a pinch point or damaged insulation, the control board will read a near-zero resistance and flag a short circuit. Look for areas where the harness routes through panels or brackets that could cause chafing.

See the test procedure for each cause

Frequently asked questions about Error4

What does Error4 mean on a LG refrigerator?
Error4 indicates the control board has detected an abnormal reading from the defrost sensor circuit, either a short circuit or an open circuit. The defrost sensor is a thermistor located near the evaporator coils that tells the board when to end the defrost heating cycle. When this sensor or its wiring fails, the board logs Error4 and normal defrost operation may be disrupted. Resistance should be checked at CON7 PIN 3 and PIN 4 to begin diagnosing the fault.
Can I fix Error4 on my LG refrigerator myself?
A knowledgeable DIYer can diagnose this error by using a multimeter to check resistance at the defrost sensor connector, CON7 PIN 3 and PIN 4. If the wiring is intact and the sensor itself reads open or shorted, replacing the defrost thermistor is a straightforward repair involving unplugging the old sensor and connecting the new one. However, accessing the evaporator and sensor typically requires removing the freezer back panel, so comfort with appliance disassembly is helpful.
Is it safe to keep using my LG refrigerator when Error4 is showing?
The refrigerator may continue to run, but without a functioning defrost sensor the appliance cannot properly regulate the defrost cycle. This can lead to ice buildup on the evaporator coils over time, which reduces cooling efficiency and can eventually cause the refrigerator to stop cooling adequately. It is best to address Error4 promptly to prevent food spoilage and potential secondary damage to other components.
Will resetting my LG refrigerator clear the Error4 code?
A reset may temporarily clear the error display, but the code will return if the underlying fault with the defrost sensor or its wiring has not been corrected. The control board continuously monitors the sensor circuit, so any persistent open or short condition will trigger Error4 again after the reset. A proper repair to the sensor or harness is required for the error to clear permanently.
How much does it cost to fix Error4 on a LG refrigerator?
If the defrost sensor is the failed component, the part itself typically costs in the range of $15 to $50 depending on the specific model. If you hire a technician, total repair costs including labor generally fall in the range of $100 to $200. Costs can be higher if the wiring harness is also damaged and requires replacement or splicing in addition to the sensor.

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