Bosch Dishwasher Error Code E21

Bosch Dishwasher E21 Error — What It Means and Why It Happens

The Bosch dishwasher E21 error code is a common fault indication on many Bosch models that generally points to a problem with water flow, drainage or related sensors. Although the exact cause can vary by series and model, E21 frequently appears when the dishwasher detects improper water movement, restricted drainage, or issues with the drain pump or water-level sensors. Users may notice symptoms such as longer cycles, incomplete washing or drying, water remaining in the tub after a cycle, unpleasant odors from standing water, and in some cases, safety risks like a persistent leak or electrical faults if the pump or board is failing.

Common Causes

• Clogged filter or debris in the sump restricting water flow
• Partially or fully blocked drain hose (kinks, food waste, foreign objects)
• Faulty or obstructed drain pump (impeller jammed or pump failed)
• Malfunctioning float switch or pressure sensor giving incorrect water-level readings
• Faulty check valve or clogged air gap/garbage disposal connection
• Loose or damaged wiring to the drain pump or sensors
• Control board (PCB) or software error reporting incorrect diagnostic status
• Model-specific sensor or flow meter failures that trigger E21

Troubleshooting Steps

1. Power Cycle: Turn off the dishwasher at the wall or breaker for 1–5 minutes, then restart to clear temporary errors and re-run a short cycle.
2. Check Error Memory / Diagnostics: If your model supports it, run the Bosch diagnostic/self-test mode to get more detailed error logs and confirm E21 is active.
3. Inspect & Clean Filters: Remove the bottom rack and clean the coarse and fine filters and the sump area. Remove debris, broken glass or food waste that could block flow.
4. Examine the Drain Hose: Pull the dishwasher forward and inspect the drain hose for kinks, clogs, or improper high-loop/air-gap configuration. Remove and flush the hose if necessary.
5. Check the Garbage Disposal / Air Gap: If connected to a garbage disposal, ensure the knockout plug was removed during installation and the disposal isn’t clogged. Clear the air gap if present.
6. Inspect the Drain Pump: Listen for abnormal pump noises during a drain cycle. Remove the lower access panel (power off first) and inspect the pump impeller and housing for obstructions.
7. Test Float Switch / Pressure Sensor: Verify the float in the base can move freely. If your model uses a pressure sensor or flow meter, inspect tubing and connectors for blockages or leaks.
8. Check Wiring & Connectors: With power off, inspect wiring to the drain pump, sensors, and PCB for corrosion, loose connections, or damage.
9. Reset and Re-run a Cycle: After cleaning and checks, run a short rinse/drain program to see if the error returns.
10. Replace Suspect Parts: If the pump, hose, float, or sensor is clearly defective, replace with OEM Bosch parts. Keep serial/model number handy when ordering.
11. Call a Pro if Needed: If E21 persists after basic checks — or if you encounter electrical faults, water leaks, or cannot access components safely — contact Bosch service or a qualified appliance technician.

Maintenance / Prevention Tips

• Clean the filter assembly weekly or as recommended in your manual.
• Run the garbage disposal before starting the dishwasher to reduce larger debris entering the drain.
• Check and straighten the drain hose periodically to prevent kinks.
• Maintain a proper high-loop or install an air gap to prevent backflow.
• Rinse heavily soiled dishes or remove large food particles before loading.
• Use the correct detergent and dose to avoid residue buildup.
• Run a monthly maintenance cycle with a dishwasher cleaner to remove grease and limescale.
• Inspect the dishwasher base for signs of leaks or standing water after cycles.
• Ensure filters are seated correctly after cleaning to avoid bypass and clogging.
• Don’t overload the dishwasher; allow free water circulation around items.
• Check hose connections and clamps are tight after any maintenance.
• Replace old or brittle drain hoses every few years to prevent collapse or cracks.
• Schedule professional servicing if the unit is aging or shows multiple recurring errors.
• Keep the user manual and model number handy for quick reference and part ordering.

FAQs

Is E21 dangerous?

E21 itself is a diagnostic code, not an immediate hazard, but the underlying cause (leaks, pump failure, electrical faults) can create safety concerns. If you see water leaking, burning smells, or sparking, turn off power and water and call a technician immediately.

Can I clear E21 by restarting the dishwasher?

Sometimes a simple power cycle clears a transient error. If E21 returns after a restart, further inspection and repair are required since the underlying issue remains unresolved.

How much will repairs cost?

Costs vary by part and labor. Cleaning filters and hoses is low cost. Replacing a drain pump or sensor is moderate; control board replacement is typically more expensive. Always get a quote and verify OEM parts for Bosch models.

Will replacing the drain pump fix E21?

If diagnostic steps show the pump is jammed or electrically faulty, replacing the drain pump often resolves E21. However, ensure there are no downstream blockages or wiring issues before replacing parts to avoid repeat failures.

Conclusion & Safety Notice

Addressing a Bosch dishwasher E21 error promptly helps prevent more serious damage, unwanted downtime, and potential safety hazards. Start with simple, safe checks—filters, hoses, and a power reset—and move to more in-depth inspection only if you are comfortable and the appliance is disconnected from power. Because dishwashers involve water and mains electricity, avoid risky DIY repairs if you lack experience. Contact Bosch service or a qualified appliance technician when in doubt, when electrical components must be accessed, or when the fault persists after basic troubleshooting.

If you need help identifying parts or finding a certified Bosch service provider, keep your appliance model and serial number ready and consult the owner’s manual for model-specific diagnostics. Safe repair or professional help will get your dishwasher back to reliable operation and avoid further issues.