Samsung C-21 Error Code | Fast & Reliable Repair

Error Code Explained

What Does the Samsung C-21 Error Code Mean?

The C-21 error code on a Samsung oven or range indicates a fault with the upper oven cavity temperature sensor (also called the oven sensor or RTD sensor). The control board monitors the sensor's resistance to track oven temperature. C-21 triggers when the sensor circuit reads outside the expected resistance range — either an open circuit (broken sensor wire or disconnected connector) or a short circuit (sensor damaged or wiring shorted to chassis).

C-21 prevents the upper oven from operating because the control board cannot regulate temperature without a functioning sensor. The oven will not heat to setpoint and may display the error immediately on preheat or during the cycle.

Root Causes

Common Causes of the Samsung C-21 Error Code

1

Failed Upper Oven Temperature Sensor

The RTD temperature sensor probe inside the upper oven cavity has failed — either an internal open circuit or a short. Sensor failure is the most common cause of C-21 and is confirmed by testing the sensor resistance with a multimeter (a good Samsung oven sensor reads approximately 1,080–1,090 ohms at room temperature).
2

Disconnected or Damaged Sensor Wiring

The two-wire harness connecting the sensor probe to the control board can pull loose from the sensor connector, especially after the oven has been moved or serviced. A damaged wire with a broken conductor also triggers C-21.
3

Wiring Harness Short to Chassis

If the sensor wiring contacts the oven cavity wall or a metal bracket, a ground short creates an out-of-range resistance reading and triggers C-21.
4

Faulty Main Control Board

In rare cases, the control board's sensor input circuit fails and misreads a good sensor as open or shorted. This is the least common cause and is only suspected after the sensor and wiring are confirmed good.

Step-by-Step Guide

How to Troubleshoot the C-21 Error Code

⚠️

Safety First: Always disconnect the Oven/Range from power before inspecting any internal components. Do not attempt electrical repairs. If in doubt, call a certified technician.

1

Locate and inspect the upper oven sensor

The upper oven sensor is typically a small probe mounted on the back wall inside the oven cavity, held by one or two screws. With the oven unplugged, remove the screws and gently pull the sensor forward to access its connector.
2

Test the sensor resistance

Disconnect the sensor connector and test across the two sensor terminals with a multimeter set to ohms. At room temperature (70°F / 21°C), a healthy Samsung oven sensor reads approximately 1,080–1,090 ohms. A reading of 0 (shorted) or OL/infinity (open) confirms sensor failure.
3

Inspect wiring from sensor to control board

Trace the sensor harness from the sensor probe to the control board connector. Check for pinched, burnt, or broken wires and ensure all connector pins seat fully. Reseat the connector at both ends.

Professional Service

When to Call a Samsung Technician

⚠ Stop DIY if any of these apply

If the sensor tests within spec and wiring is intact, the main control board requires professional diagnosis. Control board replacement on a range involves high-voltage components and should be performed by a certified technician.

Estimated Repair Cost

$90 – $310

Exact quote before any work begins. No surprises.

📞 844-739-1647

FAQ

Frequently Asked Questions — Samsung C-21

A healthy Samsung oven temperature sensor reads approximately 1,080–1,090 ohms at room temperature (around 70°F / 21°C). The resistance increases as temperature rises. A reading of zero or infinite ohms confirms the sensor has failed.
The upper oven will not operate with C-21 active. The control board disables oven heating when it cannot read a valid temperature, preventing uncontrolled heating. Surface burners on a gas or electric range are typically unaffected.
No — C-A1 indicates a short circuit in the oven sensor (resistance too low), while C-21 specifically indicates the upper oven sensor is open or out of the expected resistance window. Both involve the temperature sensor but represent different failure modes.

Book a Samsung Oven/Range Repair Appointment

Samsung specialist available same-day. We'll call within 60 minutes to confirm.

Free Diagnosis Estimate
30-Day Warranty
No Hidden Fees
Same-Day Service Available

Your information is secure. We never share or sell your data.