Sub-Zero Classic BI Code 40-8-40: Ice maker fill time exceeded

What 40-8-40 means

On Sub-Zero Classic built-in units like the BI-36U/S and BI-36UFD/S, 40-8-40 shows when the ice maker ran for its maximum fill time without collecting the water volume it needs. The control opened the fill and waited, yet not enough water arrived before the timer ran out. That points to the water supply side: low household pressure, a clogged filter or a restricted line. At the bin you may find small or hollow cubes, uneven batches, or no new ice at all.

Common causes of 40-8-40

Low household water pressure reaching the unit
Clogged or overdue water filter
Kinked, crushed or partly closed supply line
Water valve passing less water than it should

✓ One safe check you can try

1. Find the household shutoff that feeds the refrigerator and make sure it is turned fully open. 2. Replace the water filter if it is at or past its change date. 3. Without pulling the unit out, look for kinked tubing where you can see it. 4. Switch the ice maker off, wait a minute, and switch it back on to start a fresh fill.

! Why to stop there

Supply pressure has to be measured right at the unit, not at the sink.
The valve and tubing are reached behind the lower grille near wiring.
Every water joint must be remade without a slow leak behind the cabinetry.

Opening a panel yourself does not automatically cancel a manufacturer warranty, but it can cause accidental damage, and some manufacturers set their own service conditions. Check your warranty terms, or ask us, before deciding.

→Same appliance

Other Refrigerator codes

ddSub-Zero 600 and 700 Series Display dd: Diagnostics switched off deSub-Zero 600 and 700 Series Display de: Diagnostics enabled 23Sub-Zero 600, 700 and 648PRO Code 23: Defrost overheat with no feedback 50Sub-Zero 600 and 700 Series Code 50: Refrigerator compressor running too long 41Sub-Zero 648PRO Code 41: Zone compressor or wiring problem 81Sub-Zero 700-2 Code 81: Variable-Speed compressor fails to start 82Sub-Zero 700-2 Code 82: VS compressor controller needs replacement 88Sub-Zero 700TF Code 88: Board and compressor controller not talking

40-8-4040-8-40 questions

Why are my cubes small or hollow?

The ice maker gets a fixed window to fill. When water trickles in too slowly, the tray is only partly full when the window closes, so cubes freeze small or hollow and the BI control records 40-8-40.

Will a new filter clear this code?

If the old filter was clogged, a fresh one often restores full flow and the code stops returning. If it keeps coming back with a new filter, pressure or the valve needs a closer look.

What do you check during the visit?

We measure incoming pressure, inspect the line for restrictions and test the valve flow. You receive a written price before work, and the repair carries our 30-day workmanship warranty.