Error Code EC42 on a Sub-Zero ice maker machine points to a potential issue with the ice maker’s thermistor. The thermistor is a temperature sensor that plays a crucial role in monitoring and regulating the ice-making process. Here’s what you can do to diagnose and potentially address this issue:

1. Power Cycle the Ice Maker:
   Start by turning off the ice maker and unplugging it from the power source. Wait for a few minutes and then plug it back in and turn it on. Sometimes, a simple reset can clear the error code.

2. Temperature Settings:
   Verify that the temperature settings for the ice maker are within the recommended range. Incorrect temperature settings can trigger thermistor-related errors.

3. Thermistor Inspection:
   If you’re comfortable with appliance maintenance, you can visually inspect the thermistor for any signs of damage or loose connections. If you find any issues, consult your Sub-Zero user manual for guidance on replacing or repairing the thermistor.

Keep in mind that dealing with sensitive temperature sensors like the thermistor requires care and precision. If you are not experienced with appliance repairs, it’s always safer to seek the assistance of a qualified technician to ensure proper diagnosis and resolution of the error code EC42 on your Sub-Zero ice maker machine.