The display shows E04 and the machine stops; this often occurs when attempting to brew or rinse.

Safety first: Switch off and unplug the machine before removing the brew unit. Do not force any internal mechanisms.

• Remove and clean the brew unit: Open the service door, unlock, and pull out the brew unit. Rinse it thoroughly under lukewarm water, gently moving the internal piston. Allow it to dry and reinstall correctly until it clicks into place.
• Clear coffee grounds: Check the interior where the brew unit sits for loose coffee grounds or foreign objects. Carefully vacuum or wipe out any debris.
• Lubricate moving parts: Apply a small amount of food-safe silicone grease to the brew unit rails and moving joints, as recommended by Bosch.
• Reset the machine: After reinstalling the brew unit, power the machine back on and allow it to complete its self-test. Listen for the brew drive motor cycling.
• If E04 persists: The brew drive motor, gearbox, or position switch may be defective. These parts are located behind the brew chamber and require disassembly of the housing. Contact a Bosch technician if you are not experienced.