A C-21 code on a Samsung wall oven flags a problem in the temperature sensing circuit, part of the shared MICOM control family used across Samsung range, oven, and cooktop lines. The control board is reporting that the reading from the oven’s internal temperature sensor falls outside the range it expects, so it halts heating rather than risk overshooting or undershooting the set temperature.
Why this sensor failure shows up
The oven relies on a probe-style RTD sensor mounted at the back or top of the cavity to track actual air temperature and feed that data to the control board throughout a bake or broil cycle. A C-21 reading typically traces back to one of these:
- The sensor probe itself has drifted out of calibration or failed internally
- A loose, corroded, or heat-damaged connector between the sensor and the wiring harness
- A pinched or chafed sensor wire caused by repeated door use or a shifted rack
- A control board that has stopped reading the sensor signal correctly
Owner-safe steps and when to call a technician
Cut power to the oven at the breaker for a minute, then restore it — this clears a false trigger caused by a brief power fluctuation. Once power is back, run a short bake cycle and watch whether C-21 reappears immediately or only after the oven has been running for a while, since timing helps a technician tell a full sensor failure from an intermittent wiring issue.
Do not attempt to access or replace the sensor yourself; it sits inside the cavity liner behind the back wall panel and reaching it means removing insulation and, in many cases, the oven’s rear service panel. If C-21 persists after a power cycle, the sensor or its wiring needs to be tested with a multimeter against the resistance values in the service documentation, which is diagnostic work best left to a trained technician.
Our oven repair service covers Samsung temperature sensor diagnosis and replacement. General Samsung support resources are posted at samsung.com/us/support.
Independent resource — not affiliated with Samsung Electronics.
