Error Code C-21
Temperature sensor reading exceeds safe operating threshold
Critical
Stop using immediately - risk of damage or safety issue
Also displayed as: C-21
What This Means
Temperature sensor malfunction; Heater relay stuck on; Heater element failure (stuck on); Main PCB relay malfunction; Main PCB sensing circuit failure
What actually causes this:
Sensor failure, heater element stuck on, relay malfunction, or control board failure
First Thing to Check
Measure oven temperature sensor resistance (disconnect power first)
Parts Involved
How to Fix
- 1
Disconnect power and sensor harness
- 2
Measure sensor resistance (should be 1080 ohms at room temperature)
- 3
Check broil, bake, and convection heater resistances
- 4
Check DLB, broil, bake, convection relays on Main PCB for operation
- 5
Check wire harness continuity on Main PCB
- 6
Measure oven sensor connector resistance on Main PCB (normal 2850 ohms)
Other Error Codes for NQ70M9770D
Temperature sensor internal to Main PCB is not functioning
Keypad short circuit detected
Door lock mechanism malfunction or misalignment
Meat probe sensor circuit shows abnormally low resistance
Bake heating element not energizing during self-test
Main control board temperature sensor reads excessive heat
Partition configuration changed during active cooking cycle
Broil heating element not energizing during self-test