LG Microwave Error F4

⚡ Quick Answer: The LG microwave error F4 signals a malfunction in the humidity or steam sensor circuit. This can cause the microwave to display the F4 code, stop mid... ✅ DIY Fixable

What Does Error F4 Mean?

The LG microwave error F4 signals a malfunction in the humidity or steam sensor circuit. This can cause the microwave to display the F4 code, stop mid-cycle, or fail to start, particularly when using sensor cooking modes. The control board disables sensor functions due to improper sensor behavior, while manual cooking modes may still operate normally. Common symptoms include unusual humming sounds and ineffective heating.

Common Symptoms:

  • Microwave displays F4 and stops mid‑cycle or will not start
  • Error appears specifically when using sensor cook or humidity/steam based functions
  • Manual or time‑only cooking functions may still work while sensor functions fail

Possible Causes

  • Faulty humidity/steam sensor (open or shorted) (medium)
  • Control board circuit interpreting sensor data malfunction (low)

How to Fix Error F4

DIY Fix Power cycle the microwave

  1. Unplug the microwave from the power outlet.
  2. Wait 10–15 minutes to allow capacitors to discharge and electronics reset.
  3. Plug the microwave back in and attempt using a non‑sensor mode first.

Technician Only Inspect and repair humidity sensor circuit

  1. Ensure the microwave is fully unplugged and high‑voltage capacitors are discharged.
  2. Remove the cabinet and locate the humidity/steam sensor assembly.
  3. Inspect sensor wiring harness and connectors for continuity, corrosion, or damage using a multimeter.
  4. Replace faulty humidity sensor and secure wiring if defective.
  5. Test the main control board’s sensor input circuit and replace the board if sensor readings are not accepted.

Parts needed: Humidity/steam sensor assembly, Main control board (if required), Wiring harness/connectors

🛑 When to Call a Pro:
  • If the error persists after power cycling and basic checks
  • If opening the unit is required
  • If you lack tools for continuity testing

Next step

Choose the next step for F4

Confirm the diagnosis before ordering. An error code can identify the system involved, but it does not prove that a specific part has failed.

Based on diagnostic data

Most relevant component to inspect

Main Control Board

The central brain of the appliance that controls all components, cycles, and timings.

Typical part-only price
$120 - $280
DIY difficulty
Medium
Estimated time
20-40 mins
Where can I find the model number?

Check the rating label around the door, lid, frame, rear panel, or inside the appliance cabinet. Use the complete model number, including suffixes.

Find a part that fits my model

Verify the complete model and part number on the retailer's compatibility page before ordering.

Other parts options

Check related components first; use model search as a fallback.

Possible related component

Wiring Harness

Connects controls, sensors, motors, and other electrical components inside the appliance.

$20 - $120 · Medium · 30-90 mins

Check fit & price
Model number required

Model-compatible Microwave parts

Enter the complete model number to browse compatible replacement parts. This is a model-based parts search, not a diagnosis that a specific component failed.

Find a part that fits my model

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Technical Specifications

wattage 1000W
component Magnetron
resistance 0.5-1.5 ohms
part_number LG 2M246-00101
voltage_rating 120V AC

Common Questions

What does F4 error mean on lg microwave?

F4 error indicates a malfunction in the humidity sensor circuit, affecting sensor cooking modes.

Can I fix lg microwave F4 error myself?

Yes, try power cycling the microwave by unplugging it for 10-15 minutes before testing non-sensor modes.

How much does it cost to fix F4 error?

The estimated repair cost ranges from $50 to $300, depending on parts and labor.

When should I call a technician for F4?

Call a technician if the error persists after power cycling or if you lack tools for continuity testing.

Sources & References

Data last verified: 2026-07-26

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