Display shows E04 and the machine stops; often occurs when trying to brew or rinse.

Safety first: Switch off and unplug the machine before removing the brew unit. Do not force 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, moving the internal piston gently. Allow it to dry and reinstall correctly until it clicks.
• Clear coffee grounds: Check the interior where the brew unit sits for loose coffee grounds or foreign objects. Vacuum or wipe out debris carefully.
• 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 behind the brew chamber and require disassembly of the housing; contact a Bosch technician if you are not experienced.