If a Samsung microwave shows **E-21**, the verified Samsung meaning in this research set is **open temperature sensor error**. Use the code to narrow the diagnosis, then confirm the exact model because code scope can change by product generation or region. Samsung uses overlapping code conventions across model years and regions. This page keeps the appliance context attached to the code so a same-looking string from another product family is not misapplied. The recorded display form is **E-21**. Search normalization stores it as **E21** while preserving the characters a homeowner actually sees.
Reviewed by Ethan Mercer · Last reviewed August 17, 2026
Written by
Ethan Mercer Appliance Repair Content SpecialistPublished August 17, 2026Updated August 22, 2026Technically reviewed August 17, 2026
Content status:
Verified
Error codeE21
ApplianceMicrowave
Quick answer
Open temperature sensor error.
Model compatibility: Samsung can reuse or reformat codes across series and model years, so E21 may mean something different on another appliance or generation. Confirm this against your model’s documentation and record your full model number before acting.
Plain language
What this code means
If a Samsung microwave shows **E-21**, the verified Samsung meaning in this research set is **open temperature sensor error**. Use the code to narrow the diagnosis, then confirm the exact model because code scope can change by product generation or region. Samsung uses overlapping code conventions across model years and regions. This page keeps the appliance context attached to the code so a same-looking string from another product family is not misapplied. The recorded display form is **E-21**. Search normalization stores it as **E21** while preserving the characters a homeowner actually sees.
Signs
Symptoms you may notice
On affected Samsung microwave models, the control may stop or limit operation because a temperature reading is missing or implausible.
A symptom that fits E-21 is that heating, cooling, drying, or defrost behavior can become inconsistent.
When the E-21 condition is present, the display can return at a similar stage each time the affected sensor is checked.
A symptom that fits E-21 is that e-21 appears and the microwave can stop or limit the function associated with open temperature sensor error.
Why it happens
Possible causes
varies by model/region — cross-region baseline — Open temperature sensor error
Before you call
Safe checks you can make
These are simple, non-hazardous checks only. If anything is unclear, stop and contact a technician.
With E-21 recorded, record when the code appears and whether the appliance had just heated, cooled, or defrosted.
Before requesting service for E-21, confirm vents, doors, filters, and ambient conditions are normal where they affect the sensor reading.
A safe owner-level check is to use the exact model manual before assuming the sensor itself is defective.
Before requesting service for E-21, record the exact code and model number.
The next non-invasive check is to power the microwave off for 60 seconds only if Samsung's model guidance allows a reset.
The next non-invasive check is to do not remove the outer cabinet or access internal high-voltage components.
Important safety warning. Do not remove the microwave outer cabinet. High-voltage components can retain dangerous energy even after the appliance is unplugged. Do not bypass a safety device merely to see whether E-21 disappears.
Get help
When to request repair service
Persistent temperature-sensor codes usually require resistance/connection checks at the sensor, harness, and control—work best done with the model-specific service procedure. In a service visit for E-21, model-specific testing should follow the open temperature sensor error circuit rather than treating the code as proof of one failed part.
Book your repair
Seeing this code on your Samsung appliance?
Book a specialist visit for a clear estimate and approval before any repair.
One controlled restart is reasonable after correcting an obvious external issue. A recurring **E-21** display should be treated as diagnostic evidence, not as a reason to keep rebooting the appliance.
Do not keep operating the appliance through a hazardous symptom just to see whether **E-21** clears. If there is heat, water, electrical, gas, or food-safety risk, stop and arrange diagnosis.
No. **E-21** tells you which condition or check the control detected. The same display can result from the named component, its wiring, a connector, a supply/airflow/water condition, or the control that reads it.
The same-looking code can be reused on another Samsung appliance family or reformatted by region/model year. Match the appliance type and exact model before applying a meaning. This page therefore keeps **Microwave E-21** separate from same-looking codes used by other Samsung appliance families.
