Code: F4🔧 GE Microwave

GE Microwave F4 Error Code: Open Humidity Sensor (What It Means and What to Do)

Reviewed 2026-10-25 · Based on 3 manufacturer & service sources

What the code means

GE Appliances programs fault codes into its microwave controls to help technicians diagnose problems. In GE's support article "Microwave - Error, Fault or Function Codes", F4 is defined as an open humidity sensor and F5 as a shorted humidity sensor. GE's list for 240-volt Advantium ovens defines F4 as an open or shorted humidity sensor. "Open" means the control is no longer getting a reading through the sensor circuit, which usually points to a failed sensor, a loose or broken connection, or damaged wiring between the sensor and the control board. The humidity sensor detects the steam food gives off, which is how sensor cooking and sensor reheat decide when food is done. GE says that shutting off the circuit breaker or fuse feeding the microwave for 30 seconds sometimes clears a fault code, but that some cases need service, and that a trained service technician should diagnose a fault code that stays. F4 is different from the "ERR" or "SENSOR ERROR" message on GE microwaves, which GE explains is a normal message when the door is opened before steam is detected or no steam is detected within the expected time, and different from F3 (a shorted touch pad panel) and F1/F2 (the thermal sensor).

Likely causes

Safe DIY checks

⚠ Before you start

Unplug the appliance or switch off its breaker before opening panels.

  1. Press Cancel/Off (or Clear/Off) to clear F4 from the display, then try your cooking program again.
  2. If F4 comes back, turn off the circuit breaker or fuse that feeds the microwave (or unplug it) for 30 seconds, restore power and try again. GE says this sometimes clears a fault code.
  3. Until it's repaired, try heating with Cook Time (a manual time and power level) instead of sensor programs, and watch whether F4 returns.
  4. Make sure the vents aren't blocked and the cavity is clean and dry, then test with a cup of water.
  5. Don't open the case to look for the sensor. Microwaves hold a high-voltage capacitor that can stay charged even when unplugged, so sensor and wiring checks are a technician job.

🛠 When to call a pro

  • F4 keeps coming back after the 30-second power reset: schedule service. GE says a trained service technician should diagnose a fault code that won't clear, and the humidity sensor is replaced as a part matched to your model number.
  • F4 shows together with other F codes, or the microwave stops heating: have the sensor wiring and control board checked.
  • You notice a burning smell, sparks or smoke: turn off the breaker and call for repair.

Parts that commonly fix it

Always match the part number to your exact model.

⚙

Microwave humidity sensor

The part GE's fault-code list points to for F4. Match your exact model number; a technician should confirm the sensor and wiring before replacing it.

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Sources

  1. GE Appliances: Microwave - Error, Fault or Function Codes (F4: open humidity sensor; F5: shorted humidity sensor; 30-second breaker reset sometimes clears a code, some cases need service)
  2. GE Appliances: Advantium 240 Volt - Error, Fault or Function Codes (F4: open or shorted humidity sensor; Clear/Off, then 30-second power disconnect)
  3. GE Appliances: Microwave Drawer - Messages and Error Codes on the Display (ERR / SENSOR ERROR: steam not detected during sensor cooking, a normal message)

Last reviewed 2026-10-25. Always confirm against the manual for your exact model number.