Machine shows B4 and milk frothing is disabled; coffee brewing may still work.

Safety first: Steam and hot milk can cause burns. Turn OFF, unplug, and allow the frother to cool before disassembly.

Step 1 – Clean external milk components

• Remove the milk frothing nozzle, pannarello, or milk carafe (depending on model).
• Disassemble removable parts and soak them in warm water with mild detergent for 15–20 minutes.
• Use a small brush or pin to clear any blocked holes in the nozzle.
• Rinse thoroughly and reassemble.

Step 2 – Clean milk suction tube

• Inspect the silicone milk tube for clogs or dried milk.
• Flush the tube with hot water and detergent, then rinse.
• Replace the tube if it is opaque, cracked, or permanently clogged.

Step 3 – Descale steam circuit

• Run a descaling cycle focusing on the steam/hot-water outlet as per the manual.
• After descaling, run several steam cycles with clean water to flush residues.

Step 4 – Internal sensor check (advanced)

• Unplug and remove the cover.
• Locate the steam thermoblock or boiler and its temperature sensor.
• Check wiring and connectors for damage.

When to seek service

• If B4 persists after thorough cleaning and descaling, the milk temperature sensor or steam heater may be faulty and should be replaced by a technician.