Oven displays C-21 and will not heat or stops heating shortly after starting a cook cycle.

Safety first: Turn the oven off at the control panel and switch off the circuit breaker or remove the fuse before any work. Allow the oven to cool completely.

• Power reset: Turn the breaker off for 2–3 minutes, then back on. Try a simple bake cycle to see if the code clears.
• Inspect the temperature sensor:
  • Locate the oven temperature sensor probe inside the cavity (usually a thin metal rod at the back wall, upper area).
  • Check that the probe is not bent, broken, or coated in heavy grease/carbon. Clean gently with a non‑abrasive pad if dirty.
  • From the rear or top (depending on model), remove the back panel and verify the sensor wiring harness is firmly connected to the main PCB.
• Check resistance (for advanced DIYers with a multimeter):
  • Disconnect the sensor connector from the harness.
  • Measure resistance across the sensor terminals at room temperature (~77°F / 25°C). A typical Samsung sensor reads about 1050–1100 Ω at room temp.
  • If reading is open (OL), shorted (near 0 Ω), or far outside spec, replace the sensor.
• If the sensor tests good: The fault may be in the main relay control board’s sensor circuit. At this point, replacement of the main PCB is recommended and is best done by a qualified technician.