Safety: Switch off power and water before working on the appliance.

E12 indicates severe limescale issues affecting heating and water flow.

Run descaling cycle: Use a dishwasher descaler specifically recommended for Neff/Bosch/Siemens. Run a hot intensive program with the machine empty, following product instructions.
Check salt usage: Ensure the water softener salt reservoir is filled with dishwasher salt and the hardness setting is correctly adjusted for your local water hardness.
Inspect heater and heat exchanger: Remove side and base panels to visually inspect the flow-through heater and heat exchanger. Heavy white deposits indicate limescale.
Manual descaling: If accessible, remove the heat exchanger and soak it in a descaling solution until deposits dissolve. Rinse thoroughly before refitting.
Replace components: If limescale has damaged the heater or blocked channels beyond cleaning, replace the heater assembly or heat exchanger.

To prevent recurrence, always keep salt topped up and periodically run a hot cycle with descaler.

Dishwasher shows E12; often after long-term use in hard water areas, with poor drying and heating performance.

Possible Causes