ErrorCodeDoctor
LG · Microwave

LG Microwave F4 error code

Difficulty: Hard · Cost: $80–$250 · Duration: Requires professional service

The F4 error means your LG microwave has detected a problem with the humidity sensor — the component that detects steam and moisture levels inside the cavity to automatically adjust cooking time on certain settings. When it fails the microwave cannot use sensor cooking functions correctly. There are no user steps to resolve this error and the unit requires a professional repair service to inspect and replace the faulty humidity sensor.

Common causes

  • Humidity sensor has malfunctioned or failed completely
  • Wiring connection to the humidity sensor is loose or damaged
  • Internal fault in the humidity sensor circuit

How to fix it

  1. 1

    Disconnect the microwave from power for about a minute and plug it back in to attempt a reset

  2. 2

    If F4 returns after resetting the humidity sensor needs inspection and replacement by a qualified technician

Related LG Microwave error codes

1

E10

The control board has detected an internal short circuit

hard
2

F1

A fault was detected in the main control board

hard
3

F2

The thermistor detected that the temperature is out of the safe operating range

hard
4

F3

A fault was detected in the control panel

hard

F4 error — frequently asked questions

What does the F4 error mean on a LG microwave?

The humidity sensor has detected a fault

What causes the F4 error?

The F4 error is usually caused by: Humidity sensor has malfunctioned or failed completely; Wiring connection to the humidity sensor is loose or damaged; Internal fault in the humidity sensor circuit.

Can I fix the F4 error myself?

This is rated a hard fix — it often requires tools, parts, or experience, and may be safer left to a professional technician.

How much does it cost to fix the F4 error?

Fixing the F4 error on a LG microwave typically costs $80–$250, depending on parts and whether you do it yourself or hire a technician.

Is it safe to keep using my microwave with the F4 error?

We'd recommend addressing the F4 error before continuing to use the microwave, since hard-rated issues often involve a real fault rather than a minor glitch.