Dishwasher shows E04 and may have poor spray performance or unusual spray patterns.

Safety first: Turn off power and water supply before working on the dishwasher.

• Clean filters: Remove the lower rack and twist out the Bosch filter assembly (coarse and fine filters). Rinse thoroughly under running water and remove any debris from the sump.
• Inspect spray arms: Remove upper and lower spray arms. Rinse and clear all jets with a toothpick or small brush. Ensure the arms spin freely when reinstalled.
• Check diverter valve: Many Bosch models use a diverter motor integrated into the circulation pump/heat pump to direct water to different spray levels. Listen during operation for clicking or cycling sounds. If the valve is stuck, the unit may show E04.
• Run a test cycle: After cleaning, run a short cycle. If E04 persists, the diverter valve or flow sensor may be defective and the entire circulation pump/heat pump assembly may need replacement.
• Professional service: Replacing the diverter or heat pump assembly involves removing the dishwasher, tipping it, and disconnecting hoses and wiring. If unsure, contact a Bosch technician.