Sub-Zero Refrigerator Error Code 40 8 40

Error code 40 8 40 means the ice maker ran through its maximum fill time without receiving enough water to complete a fill cycle. The control monitors how long the water inlet valve stays open and logs this fault when the volume target is not met within that window. Ice production will stop until the underlying water supply issue is corrected. The problem is most often related to a clogged water filter, low water pressure, or a restricted inlet valve.

A reset may temporarily clear the fault code from the display, but it will not resolve the underlying cause. If the water supply problem is not corrected, the ice maker will attempt another fill cycle, time out again, and the error will return. Always address the root cause before or after resetting the unit.

Repair costs vary depending on the cause. Replacing a water filter is typically in the range of $50 to $100 for the part. A new water inlet valve, including parts and labor, generally runs between $150 and $350. If the ice maker module itself requires replacement, costs can range from $300 to $600 or more depending on the model and labor rates in your area.

Start by checking the water supply line behind the refrigerator for kinks, then replace the inline water filter if it is past its service interval. Verify that your household water pressure is sufficient at the supply connection. If those steps do not resolve the issue, inspect and test the water inlet valve for blockage or electrical failure, as it may need to be replaced.

This error is not a safety hazard. It simply means the ice maker has stopped operating because it cannot fill with water correctly. The refrigerator's cooling and food preservation functions are not affected by this fault. You can continue using the refrigerator normally while you diagnose the ice maker issue.