40/1/40 on a Sub-Zero Classic Built-In Series unit means the compressor ran for an excessive, abnormal length of time without cycling off — confirmed directly by Sub-Zero’s own support documentation.
Step 1: Try the Breaker Reset
Turn the home circuit breaker for the unit off for 30 seconds, then back on, and retest — this is Sub-Zero’s own recommended first step.
Step 2: Check the Obvious First
While you’re at it, check the door seal with a dollar-bill test and confirm the condenser coil isn’t visibly caked in dust — both are common, fixable triggers.
Step 3: Note Whether It Returns Immediately
If 40/1/40 comes right back after the reset, that confirms a genuine problem rather than a temporary condition.
Step 4: Book Service
Per Sub-Zero’s own guidance, no further homeowner troubleshooting is available once the reset fails. Visit our refrigerator repair page.