Machine displays E03 and stops brewing; pump may run briefly then shut off.

Safety: Turn off and unplug the machine. Allow it to cool fully before touching the boiler or internal components.

• Reset and observe: After cooling, power the machine back on. If E03 appears again during warm‑up, proceed with descaling and sensor checks.
• Descale the hydraulic circuit: Prepare a manufacturer‑approved descaling solution. Fill the reservoir with solution, run several brew cycles without coffee to flush the brew boiler, then rinse thoroughly with fresh water. Heavy scale can cause hot spots and false overheat conditions.
• Inspect the NTC sensor: Access the brew boiler temperature probe. Check for loose wiring, corrosion, or mineral buildup around the probe. Clean the probe area and reseat the connector. If the error persists, replace the NTC sensor.
• Check water flow: Ensure the vibration pump or rotary pump is delivering water to the brew boiler. A blocked inlet filter, clogged flowmeter, or stuck solenoid valve can reduce flow and cause overheating. Clean or replace the affected component.
• Control board relay: If the heater remains energized when it should be off, the heater relay may be stuck closed. This is a serious fault; replace the main control board.

Warning: Do not bypass thermostats or sensors. They are critical safety devices.