Bosch Microwave E-04: Over-the-Range Humidity Sensor Not Reporting

What E-04 means

On a Bosch over-the-range microwave, E-04 is listed as a humidity problem. Those models judge when food is ready by sensing the steam it gives off, which powers the sensor-cook and auto-reheat programs. When the humidity sensor does not report sensible values, those automatic programs stop working. Timed cooking carries on as usual, so the microwave is still useful while you sort it out.

Common causes of E-04

Grease or cooking residue coating the humidity sensor
Grease filters clogged, blocking the airflow
Humidity sensor or its wiring failed

✓ One safe check you can try

1. Make sure the cavity is dry. 2. Check that the vent grilles on top are not clogged. 3. Clean or replace the grease filters underneath, since saturated ones trap the steam the sensor needs. 4. Try a timed cook first, then a sensor program. If E-04 stays, call us.

! Why to stop there

The sensor is inside the housing, near parts that stay charged after unplugging.
Replacing the sensor will not help if saturated filters are the real cause.
Spraying cleaner into vents can reach the electronics and create a bigger repair.

Opening a panel yourself does not automatically cancel a manufacturer warranty, but it can cause accidental damage, and some manufacturers set their own service conditions. Check your warranty terms, or ask us, before deciding.

→Same appliance

Other Microwave codes

E1Bosch Microwave E1: Thermistor Circuit Reads Open E4Bosch Microwave E4: The Thermistor Circuit Reads Shorted E-11Bosch Microwave E-11: Over-the-Range Key Read as Held for a Minute ER11Bosch Microwave ER11: A Control Key Is Jammed E2Bosch Microwave E2: The Safety Shutoff Stopped Your Cycle E3Bosch Microwave E3: Door Will Not Latch or Release Properly E11Bosch Microwave E11: Moisture Detected at the Control Panel E17Bosch Microwave E17: The Fast Preheat Did Not Finish

E-04E-04 questions

Can I still cook with E-04 showing?

Yes, timed cooking should still work. Only the sensor-driven programs, such as auto-reheat, are affected by this code. Use manual times until the sensor has been checked and the microwave is working normally again.

Do greasy filters really affect the sensor?

They can. Saturated filters trap steam before it reaches the sensor, so it reads poorly. Cleaning or replacing them is inexpensive and a sensible first step.

When should I call about E-04?

If clean filters and a dry cavity do not help, the sensor or its wiring may have failed. We diagnose it, quote in writing before work, and warranty our repair for 30 days.