Dishwasher displays E12 and may have limescale buildup or poor heating performance.

Safety first: Ensure the dishwasher is empty before running cleaning cycles.

• Run descaling cycle: Use a Bosch-approved dishwasher descaler or a citric-acid-based cleaner. Run a hot, intensive cycle without dishes to dissolve limescale from the heater and internal surfaces.
• Check water hardness setting: Refer to the user manual to set the correct water hardness level in the control panel so that the built-in softener regenerates properly.
• Refill salt reservoir: If your Bosch model has a salt compartment, ensure it is filled with dishwasher salt and that the cap is tight.
• Clean heat exchanger: On models with a side heat exchanger, inspect for visible scale or blockages in the side tank. Rinse if accessible.
• Repeat cleaning: In hard water areas, multiple descaling cycles may be needed. If E12 persists, the heater or softener system may require professional service.