Symptoms
• Machine displays E04 error code on the digital display panel
• Brew cycle fails to start or stops mid-cycle
• No water flows during attempted brewing
• Machine emits warning beep or alarm sound
• The espresso group head or brew unit does not move or respond
• Hot water/steam function may also be unavailable
• Machine powers on but remains unresponsive to button commands
Possible Causes
• Internal sensor failure or malfunction in the brew unit or water circulation system
• Loose or corroded electrical connection within the machine's circuit board
• Faulty water flow sensor due to mineral buildup from hard water common in USA regions
• Malfunctioning brew unit motor or solenoid valve
• Damaged internal wiring or connector failure
• Software glitch or corrupted machine memory
• Power supply issue related to 120V/60Hz North American electrical standard
• Blocked water line or valve preventing proper sensor communication
Safety Checks You Can Do
• Check that your home circuit breaker has not tripped and that the outlet providing power to the machine is functioning properly
• Unplug the Bosch coffee machine from the electrical outlet for 60 seconds, then plug it back in to perform a hard reset
• Empty and refill the water tank with fresh, filtered water and ensure it is fully seated in the machine
• Run a descaling cycle using Bosch-approved descaling solution to remove mineral buildup common in hard water areas across the USA
• Open the brew unit access door and visually inspect for any visible debris, coffee grounds, or mineral deposits blocking the sensor area
• Remove the drip tray and grounds container, empty them completely, and check for overflow or blockages
• Verify that the brew unit is fully inserted and locked in place according to the machine manual
• Check the bean hopper for any jammed or empty beans, and manually rotate the grinder to ensure it moves freely
• Allow the machine to sit unplugged for an additional 30 minutes before attempting to power it back on
• Ensure all external water and power connections are secure and free from visible damage
Safety First
Always disconnect the appliance from power before performing any checks. If you are unsure about any step, please contact a qualified technician.