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Error code reference

Whirlpool Microwave Error Code F4E4

Humidity sensor failure

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Humidity sensor failure. There is a delay of approximately 1 minute 20 seconds before F4E4 is displayed.

First step from the service manual

Unplug microwave oven or disconnect power, then connect a new humidity sensor to the PCBA at P6.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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What F4E4 means on a Whirlpool microwave

F4E4 indicates the control board has detected a failure in the humidity sensor circuit. The humidity sensor (also called a moisture sensor) sends real-time steam level readings to the control board during cooking cycles, allowing the microwave to automatically adjust cook time. When the board cannot receive a valid signal from this sensor, it throws F4E4 and halts auto-sensing cook functions. The diagnostic check using CANCEL-CANCEL-START followed by pressing COOK will display the live sensor reading; a reading of '8891' confirms the sensor is within spec. Any other value, or no reading at all, points directly to the sensor or its wiring as the fault source.

For homeowners, this error means the part of your microwave that detects steam and moisture during cooking is not working correctly. Many Whirlpool microwaves use this humidity sensor to run features like sensor cook and auto-reheat, which automatically stop cooking when enough steam is detected. With F4E4 active, those automatic features will not function reliably. You can often still use the microwave on timed manual cook settings, but the sensor-based cooking programs should be avoided until the fault is resolved.

The humidity sensor is a relatively small component, typically mounted near the interior cavity and connected to the control board via a wiring harness. Failures stem from a degraded sensor, a broken or corroded connector, or damaged wiring between the sensor and the board.

Source: manufacturer service documentation.

Common causes of F4E4

  1. 01

    Failed humidity sensor

    Part replacement

    The humidity sensor itself has degraded or failed internally, producing a signal outside the valid range or no signal at all. This is confirmed when the diagnostic mode displays a reading other than '8891'.

  2. 02

    Damaged or disconnected wiring harness to humidity sensor

    Wiring / connection

    The connector or wiring between the humidity sensor and the control board can become loose, corroded, or physically damaged, interrupting the signal and triggering F4E4. Inspecting and reseating or replacing the harness may resolve the code without replacing the sensor itself.

  3. 03

    Corroded or burned sensor connector pins

    Wiring / connection

    Steam exposure inside the microwave cavity can corrode the connector pins at the humidity sensor or at the control board, causing intermittent or complete signal loss. Cleaning or replacing the connector resolves this if the sensor and board are otherwise intact.

  4. 04

    Faulty control board

    Part replacement

    If the humidity sensor and all wiring check out correctly but F4E4 persists, the control board may have failed in the circuit that reads the sensor signal. This is the least likely cause and should only be considered after the sensor and wiring are confirmed good.

See the test procedure for each cause

Frequently asked questions about F4E4

What does F4E4 mean on a Whirlpool microwave?
F4E4 means the control board has detected a humidity sensor failure. The humidity sensor monitors steam levels inside the cavity to control automatic cooking features. When the board cannot read a valid signal from the sensor, it logs F4E4 and disables sensor-based cooking modes.
How do I fix F4E4 on a Whirlpool microwave?
Start by entering Diagnostics mode: press CANCEL, CANCEL, then START, then press COOK to display the humidity sensor reading. If the display shows anything other than '8891', the humidity sensor needs to be replaced. Before replacing it, inspect the wiring harness and connector for loose connections or corrosion, since a bad connection can produce the same code. If the wiring is intact and the sensor reading is still wrong, replacing the humidity sensor is the correct fix.
Can I still use my Whirlpool microwave with the F4E4 error code active?
You can typically still run the microwave using manual timed cooking modes, since those do not rely on the humidity sensor. However, any sensor cook, auto-reheat, or moisture-based automatic programs will not function correctly and should not be used until the fault is repaired. Continuing to use sensor-based programs with a failed sensor may result in overcooked or undercooked food.
How much does it cost to fix a Whirlpool microwave F4E4 error?
The humidity sensor part itself typically costs between $20 and $60 depending on the model. If you are comfortable disassembling the microwave and working with small electrical connectors, this is a DIY-friendly repair. Professional labor to diagnose and replace the sensor generally adds $75 to $150 in service charges. If the control board is found to be the cause instead, board replacement costs can range from $100 to $250 for the part alone, making professional diagnosis worthwhile before committing to that repair.
How do I run the diagnostic test for F4E4 on a Whirlpool microwave?
Press CANCEL twice, then press START to enter Diagnostics mode. Once in diagnostics, press COOK to pull up the humidity sensor reading on the display. A reading of '8891' means the sensor is functioning within the acceptable range. Any other value confirms the sensor or its wiring circuit is faulty and the sensor should be replaced.

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