Ice maker displays EC40 or service code 40 and stops producing ice or produces very little ice.

Safety first: Disconnect power to the ice maker at the breaker or by unplugging the unit before removing any panels. Shut off the water supply if you will be working near water lines.

Steps to check and address EC40:

• 1. Power reset: Turn off power to the ice maker for 5 minutes, then restore power and see if EC40 clears. If it returns, continue.
• 2. Access the evaporator thermistor: Remove the front grille and lower access panel. On Sub-Zero ice makers, the evaporator thermistor is typically clipped to the evaporator plate or tubing near the freezing surface. Consult the tech sheet behind the grille for exact location.
• 3. Inspect the sensor and wiring: Look for broken insulation, corrosion at the connector, or a loose plug at the main control board. Reseat the connector firmly.
• 4. Test the thermistor: With power still off, disconnect the thermistor from the harness and measure resistance with a multimeter. Compare the reading to the Sub-Zero temperature/resistance chart (commonly included on the tech sheet). If the value is far out of range for the actual evaporator temperature, the thermistor is defective.
• 5. Replace if faulty: If readings are incorrect or intermittent when you gently wiggle the wires, replace the evaporator thermistor with a Sub-Zero OEM part. Route the new sensor exactly as the original and secure it with the factory clip.
• 6. Check the control board: If the thermistor tests good but EC40 persists, inspect the main control board for burned spots or damaged pins. At this point, professional diagnosis is recommended, as the board may need replacement and reprogramming.

When to call a technician: If you are not comfortable using a multimeter or accessing internal components, or if a control board fault is suspected, contact a Sub-Zero authorized service provider.