How to Fix LG Microwave Error F4

Error Code: F4 Difficulty: Moderate

Problem: This indicates a humidity sensor fault.

How to Fix F4 Error (Step-by-Step)

1. Begin by unplugging the microwave from the electrical outlet and confirm the error stays cleared during a full test cycle.
2. Remove the outer metal cabinet by unscrewing it from the rear and side panels.
3. Find the humidity sensor, which is typically a small rectangular component located in the air duct path, often near the top of the cooking cavity.
4. Carefully unplug the wire harness that connects to the sensor.
5. Remove the screw that fastens the sensor to the microwave chassis and remove the faulty sensor.
6. Position the new humidity sensor (part 6501W1A013A) and secure it with the screw.
7. Reconnect the wire harness, put the cabinet back on, and test a sensor cook feature to ensure the new part is working.
8. Turn the appliance off, wait about 2 minutes, then turn it back on.

Still Not Working?
If the replacement part didn’t fix the issue, you may have a wiring problem or main board failure.