Machine displays E04 and stops brewing; sometimes accompanied by unusual pump noise.

Safety first: Unplug the coffee maker. Allow it to cool before opening the housing.

Steps:

• Check water tank and filters: Ensure the tank is full and seated. Remove any removable inlet filter or mesh at the tank outlet and rinse it under running water.
• Descale: Run a descaling cycle if the machine can still start one. Scale buildup can cause the pump to stall and trigger E04.
• Listen to the pump: Plug in and start a cycle briefly. If the pump hums loudly but no water moves, there may be a blockage. Stop and unplug again.
• Access the pump: Remove the back or bottom cover. Locate the vibration pump (typically a metal cylinder with two hoses and two electrical terminals).
• Check hoses and non-return valve: Inspect the silicone hoses for kinks or blockages. Some Tefal models have a small non-return valve near the pump inlet; remove and flush it with water.
• Electrical check (advanced): With the unit unplugged, disconnect the pump terminals and measure coil resistance. Typical values are 1–2 kΩ. An open circuit or very low resistance indicates a failed pump.
• Reassemble and test: Reconnect hoses and wiring, reassemble covers, and test. If E04 persists and the pump does not run or is extremely noisy, replacement of the pump is recommended.