Bosch Dishwasher Error Code E20

Bosch Dishwasher E20 Error — What It Means

The Bosch dishwasher error code E20 most commonly points to a problem with the appliance’s heating or temperature sensing system. On many Bosch models the code appears when the dishwasher detects that water isn’t being heated correctly or the control detects an abnormal temperature reading. That can cause poor wash performance and longer cycles, damp or soggy dishes after the cycle ends, and in some cases the machine may halt mid‑cycle and display the code. While E20 is typically not an immediate fire risk, unresolved heating faults can reduce sanitization effectiveness, increase energy use, and — if caused by a shorted component — present an electrical hazard. Identifying the root cause quickly helps restore normal operation and avoids further damage to the wash motor, pump and electronic control board.

Common Causes

• Faulty heating element (open circuit or shorted)
• Defective temperature sensor (NTC thermistor) giving incorrect readings
• Loose, corroded, or damaged wiring/connectors to heater or sensor
• Failed heater relay or triac on the control board
• Control board (PCB) fault or software anomaly
• Scale or mineral buildup insulating the element and preventing proper heat transfer
• Low incoming water temperature or supply issues that make the heater run longer

Troubleshooting Steps

1. Reset the dishwasher: Turn off power at the circuit breaker or unplug for 60 seconds, then restore power. Some errors clear after a reset and allow one more cycle to test.
2. Run an empty diagnostic or heat cycle: On some Bosch models a service or intensive cycle forces the heater on; note whether the element warms and if the code returns.
3. Check for visible issues: Remove kickplate and inspect wiring, connectors, and the heater assembly for corrosion, burns, or loose plugs.
4. Measure heating element continuity: With power OFF and element disconnected, use a multimeter to check resistance (typical dishwasher heater values often range from ~10–30 ohms; consult model documentation). An open or wildly out‑of‑range reading indicates a bad element.
5. Test the NTC temperature sensor: Measure the thermistor resistance at room temperature and compare to Bosch specifications (or look for a steady resistance reading that changes smoothly with heat). Erratic or infinite readings mean replacement.
6. Inspect/clean the heater area: Remove scale or heavy deposits that could prevent proper heating. Hard‑water buildup can cause symptoms without a failed part.
7. Check the control board and relays: If heater and sensor test OK, the relay or driver on the PCB may be stuck. Visual check for burnt traces, bulging capacitors or heat damage; replace board if necessary.
8. Verify incoming water temperature and supply: Very cold inlet water can make heating take longer. Ensure proper hot water feed and pressure per Bosch specifications.
9. If unsure or if electrical tests are required, call a qualified appliance technician: Heating components are mains‑powered — avoid DIY work unless you have electrical experience.

Maintenance / Prevention Tips

• Run a high‑temperature wash periodically to help dissolve grease and reduce deposits.
• Use dishwasher cleaner or a descaler monthly if you have hard water.
• Keep filters and spray arms clean so cycles complete normally and heaters aren’t over‑stressed.
• Use manufacturer‑recommended detergents and rinse aids; buildup from incorrect products can insulate the heater.
• Avoid overloading the dishwasher to ensure proper water circulation and heat transfer.
• Inspect door seals and base for leaks; moisture near electronics can cause faults.
• Check the wiring and connectors during routine maintenance for corrosion or looseness.
• Have the appliance serviced if you notice unusual noises, burning smells, or repeated error codes.
• Ensure the electrical supply is stable and grounded to avoid control board damage.
• Keep the area under the dishwasher dry and free of debris that could hide leaks.
• Replace worn or brittle wiring harnesses before they fail.
• Follow Bosch recommended maintenance in your user manual for long‑term reliability.

FAQs

Conclusion / Safety Notice

If your Bosch dishwasher shows E20, start with simple checks (reset, visual inspection, filter cleaning) but treat heater and control diagnostics with caution. Heating elements and control boards operate on mains voltage; improper handling can cause electric shock or further damage. If tests require live measurements or complex disassembly, stop and contact a qualified appliance technician or Bosch‑authorized service.

For safe and reliable repair: document the model and serial number, note when the code appears, and share any unusual behavior with your service professional. Timely professional diagnosis helps avoid costly replacements and keeps your dishwasher operating safely.