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Error code reference

LG Cooktop Error Code F4

Right front top thermistor fault.

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Right front top thermistor fault.

First step from the service manual

Check CN 04 (Right Module); thermistor should read 500~550 K ohms at room temperature.

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

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What F4 means on a LG cooktop

The F4 error code on an LG cooktop indicates a fault in the right front top thermistor circuit. The thermistor is a temperature-sensing resistor embedded near the right front burner zone that continuously monitors surface temperature and feeds that data to the induction or radiant control module. When the control module detects a resistance reading outside the expected range for the thermistor, it triggers the F4 code and disables the affected zone as a protective measure.

The starting point for diagnosing this fault is connector CN 04, which serves the right burner module. At room temperature, the thermistor should measure between 500 and 550 K ohms. A reading significantly above or below this range confirms the sensor has failed. A reading of zero or near-zero suggests a short circuit in the thermistor or its wiring harness, while an open circuit reading indicates a broken wire or a completely failed sensor element.

Common causes include a thermistor that has drifted out of specification due to heat cycling over time, damaged wiring between the sensor and CN 04, or a loose or corroded connector at the module. In some cases the control module itself can misread a signal, but component-level failure of the thermistor or its harness is the more frequent culprit. Proper diagnosis requires a multimeter check at CN 04 before any parts are replaced.

Source: manufacturer service documentation.

Common causes of F4

  1. 01

    Failed right front thermistor

    Part replacement

    The thermistor itself has drifted out of its specified resistance range of 500 to 550 K ohms at room temperature due to heat stress or age. This is confirmed by measuring resistance directly at CN 04 and finding a value significantly outside that range.

  2. 02

    Loose or corroded connector at CN 04

    Wiring / connection

    A poor connection at the CN 04 right module connector can cause intermittent or incorrect resistance readings that trigger F4. Inspect the connector for corrosion, bent pins, or incomplete seating and reseat it firmly before replacing any parts.

  3. 03

    Damaged thermistor wiring harness

    Part replacement

    The wire leads running from the thermistor to CN 04 can sustain damage from heat exposure or pinching during a previous repair. Inspect the harness along its full length for burned insulation, breaks, or chafing.

  4. 04

    Short circuit in the thermistor circuit

    Part replacement

    A near-zero resistance reading at CN 04 indicates a short, either within the sensor itself or in the wiring. This will cause the module to read an abnormally high temperature and disable the burner zone immediately.

  5. 05

    Faulty right burner control module

    Part replacement

    If the thermistor and all wiring check out within specification at CN 04, the control module may be misinterpreting a valid signal. Module failure is the least common cause and should only be considered after the sensor and harness have been ruled out.

See the test procedure for each cause

Frequently asked questions about F4

What does F4 mean on a LG cooktop?
The F4 code on an LG cooktop indicates a fault with the right front top thermistor, which is the temperature sensor for that burner zone. The cooktop's control module monitors this sensor continuously and shuts down the right front zone when the resistance reading falls outside the expected range. At room temperature, the thermistor should measure between 500 and 550 K ohms at connector CN 04. Any reading significantly outside that range points to a sensor or wiring problem.
Can I fix the F4 error on my LG cooktop myself?
A knowledgeable DIYer comfortable with a multimeter can perform the initial diagnosis by checking resistance at connector CN 04. If the thermistor reading is out of range, replacing the sensor is a feasible repair for someone familiar with appliance disassembly. However, if the wiring harness is damaged or the control module needs replacement, the repair becomes more complex and may warrant a qualified technician.
Is it safe to use my LG cooktop while the F4 code is active?
The right front burner zone will typically be disabled when F4 is active, which is the cooktop's built-in protective response. You should not attempt to bypass this lockout or continue using the affected zone until the fault is resolved. Other burner zones may still function normally, but the underlying sensor issue should be diagnosed and corrected before relying on the appliance for regular use.
Will resetting the cooktop clear the F4 error code?
A power reset by unplugging the cooktop or cycling the circuit breaker may temporarily clear the F4 display, but the code will return if the thermistor or its wiring is genuinely out of specification. A reset alone does not correct a failed sensor or a damaged harness. Proper diagnosis at CN 04 is necessary to determine whether a component replacement is required for a lasting fix.
How much does it cost to repair an F4 error on an LG cooktop?
Repair costs vary depending on which component has failed. A replacement thermistor is typically the least expensive part, while a control module replacement will cost considerably more. When factoring in professional labor, total repair costs can range from around $100 to $350 or more depending on your location and the specific parts needed. Getting a diagnostic visit from a qualified technician will give you a more precise estimate before committing to the repair.

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