Dishwasher shows E20 and may not circulate water properly; sometimes noisy pump.

Safety first: Disconnect power and water supply. Be prepared for some water spillage when removing hoses.

• Listen for pump operation: During wash, if you hear only humming or no sound and E20 appears, the circulation pump may be jammed or failed.
• Access pump: Remove the toe-kick and side panel, then access the circulation pump/heat pump assembly under the tub.
• Check for obstructions: Disconnect the pump from the sump and inspect the impeller area for glass, bones, or other debris. Remove any foreign objects.
• Spin impeller: Ensure the impeller spins freely by hand. If stiff or seized, the pump must be replaced.
• Test motor windings: Measure resistance across the pump motor terminals. An open circuit or very low resistance indicates a bad motor.
• Replace pump assembly: Install a new Bosch circulation pump/heat pump assembly if the original is defective.