What E-04 Means
E-04 on a Bosch over-the-range microwave is listed in the service manual's fault code table as a humidity malfunction. These models use a humidity sensor to run sensor-cook and auto-reheat programmes, judging when food is done by the steam it gives off. When that sensor is not reporting sensibly the automatic programmes are the part that stops working, while timed cooking continues.
Common Causes of E-04
- Humidity sensor contaminated with grease or cooking residue
- Blocked or saturated grease filters affecting airflow
- Humidity sensor or its wiring failed
🔧 One Safe Check You Can Try
Make sure the cavity is dry and the vent grilles above the appliance are not blocked by grease-laden filters, then try a timed cook rather than a sensor programme. Clean or replace the grease filters underneath, since saturated filters trap the steam the sensor needs to read.
⚠ Why You Shouldn't Go Further Than That
- The high-voltage capacitor inside any microwave holds a charge after the appliance is unplugged and must be discharged by someone trained to do it.
- Over-the-range models are mounted above a cooking surface at head height, and dropping one during removal is a genuine hazard.
- The humidity sensor sits in the exhaust path, which means opening the cabinet to reach it.
- Cleaning the sensor element itself with a solvent damages it, so it is not something to attack with a cloth and cleaner.
Opening a panel to inspect or repair something yourself doesn't automatically cancel your manufacturer's warranty — but it can risk accidental damage, and some manufacturers do have specific service conditions. Check your product's warranty terms, or ask us, before deciding.