Microwave shows E4 and will not start any cooking program.

Safety first: Disconnect the appliance from mains before opening any panels.

• Step 1 – Clean the cavity: Wipe down the interior of the microwave, especially the area near the steam outlet and sensor window (often on the top or side of the cavity). Use a mild detergent and a soft cloth; remove grease and food splatter.
• Step 2 – Dry thoroughly: Leave the door open for at least 30 minutes to allow moisture to evaporate. Then plug the unit back in and test.
• Step 3 – Access humidity sensor (if accessible): Remove the outer cover. Locate the humidity/steam sensor module, usually near the air duct above the cavity. Inspect for corrosion, condensation, or loose connectors. Reseat the connector to the control board.
• Step 4 – Visual inspection: If the sensor housing is cracked or heavily corroded, it should be replaced with an OBH Nordica-compatible humidity sensor module.
• Step 5 – Control board check: If a new sensor does not clear E4, the fault may be on the main PCB. Further diagnosis requires professional tools and should be done by a service center.