Display shows ERR4 and brewing stops mid-cycle or does not start.

Safety first: Unplug the coffee maker before attempting any checks.

• Bleed air from the system: Fill the water tank completely. Plug the machine back in, then start a hot water or rinse cycle (if available). Open the steam/hot water knob (on models with a steam wand) to help purge air. Let the pump run for 20–30 seconds even if flow is weak.
• Descale aggressively: If the pump is noisy but little or no water comes out, limescale may be restricting flow. Run a full descaling cycle, then a second one if the machine is heavily scaled.
• Check for leaks or drips: Remove the drip tray and look underneath while the pump runs. Water leaking inside can indicate a cracked hose or blocked outlet.
• Listen to the pump: A completely silent pump when a coffee or hot water cycle is started suggests an electrical fault. In this case, internal testing and likely pump replacement are required.

Because ERR4 often involves mains-voltage components, further diagnosis should be left to a qualified technician.