Monogram Dishwasher C4 Error: Temperature sensor fault
The C4 error code indicates a fault with the water temperature sensor (NTC thermistor) inside the dishwasher. The control board is receiving a reading from the thermistor that is outside the acceptable range — either an open circuit, a short circuit, or an implausibly high or low temperature value.
~35%
DIY Fixable
From $150
Typical Repair Cost
1–2 hrs
Pro Repair Time
Quick Assessment
Answer to continue safely
Is it safe to keep using?
Maybe. The dishwasher will mechanically wash dishes, but the sanitize and heated dry functions are unreliable. Avoid using sanitize cycles until the sensor is repaired.
Can I reset the code?
Yes. A power reset may clear the fault temporarily, but if the thermistor has genuinely failed, the C4 code will return during the next heated cycle.
When to stop immediately?
Stop if you notice: Stop using the sanitize cycle entirely if C4 is active, as the board cannot guarantee the required 155°F rinse temperature without a working sensor., Stop and request service if the fault returns consistently on every cycle after a reset, confirming a hardware failure rather than a transient glitch..
Symptoms You May Notice
Dishes not fully sanitized or dried properly
Without accurate temperature data, the control board cannot regulate water heating correctly, resulting in dishes that are not sanitized and a heated dry cycle that is ineffective.
C4 displayed on the control panel
The fault code appears during the wash or rinse phase when the board attempts to read the thermistor and receives an out-of-range signal.
Cycle stalls during the heating portion
The appliance may pause indefinitely during a heated wash or sanitize cycle because the board is waiting for a valid temperature confirmation that never arrives.
No steam visible at cycle end
When the heated dry or sanitize functions cannot be confirmed through sensor feedback, the appliance may skip heating entirely, resulting in no visible steam when the door is opened.
Possible Causes
Failed NTC thermistor
The thermistor is a small resistive sensor mounted in the tub sump. Over time the sensor element degrades, producing resistance values outside the range the control board accepts.
Requires ProfessionalLoose or corroded thermistor wiring connector
The wiring harness connecting the thermistor to the control board can develop a loose pin or corroded terminal, causing an intermittent or open circuit that mimics a failed sensor.
Requires ProfessionalFaulty control board
In rare cases the analog input on the control board that reads the thermistor signal fails, causing the board to misinterpret a perfectly good sensor as faulty.
Requires ProfessionalSafe Checks You Can Do
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1
Perform a power reset
Cut power to the dishwasher at the circuit breaker for 60 seconds, then restore power. An intermittent electrical spike can sometimes cause a one-time thermistor fault that clears on reset.
If the code does not return after a full test cycle, monitor for recurrence over the next several cycles.
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2
Check the hot water temperature at the tap
Run the hot water at the kitchen sink until it reaches maximum temperature. Measure with a thermometer or simply confirm it is very hot to the touch. The dishwasher supply should be at least 120°F.
If entering the dishwasher with already-hot water, the thermistor reading will be within range sooner, reducing the chance of a timeout-related fault.
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3
Inspect the thermistor connector for corrosion
Remove the lower spray arm and filter assembly to access the sump area. Locate the thermistor (a small two-wire sensor) and check that its wiring connector is firmly seated and free of corrosion or discoloration.
Do not attempt to remove the thermistor itself without confirmed diagnosis — the part must be tested with a multimeter before replacement.
Tools required
When to Call a Professional
Contact a qualified technician if:
- The C4 code returns every cycle despite a clean power reset, indicating a failed thermistor or control board input.
- Inspection reveals a burned, cracked, or visibly damaged thermistor sensor body or connector.
Need Professional Help?
Find qualified technicians in your area for proper diagnostics and repair.
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