Microwave displays F4 and will not start or stops mid-cycle.

Warning: Microwaves contain high-voltage components. Unplug the unit and do not touch the high-voltage section.

• Reset: Unplug for 5–10 minutes, then plug back in. If F4 returns when using sensor functions, the sensor is suspect.
• Clean sensor area: Inside the cavity, locate the sensor cover or grill (often on the upper left/right). Clean off any heavy grease or food buildup that may affect sensor readings.
• Check connections: If you can safely remove the outer cover, inspect the sensor wiring and connector for loose or corroded pins. Reseat the connector.
• Replace sensor: If F4 persists, replace the humidity/temperature sensor assembly specific to your GE model.
• Control board check: If a new sensor does not resolve the issue, the main control board sensor circuit is likely defective and should be replaced by a qualified technician.