Sub-Zero error codes: what they mean and what to do
Most Sub-Zero error codes mean one of four things: a compressor that has run for too long (codes 40, 40 1 40, 40 2 40, 40 3 40 and 50), a defrost fault (21 and 24), a failed temperature sensor (EE) or an ice maker water fault (EC30). This guide from LE Company, Sub-Zero repair engineers in London, lists what each code means according to Sub-Zero’s own help pages, what you can safely do yourself, and when to call an engineer. For repairs, see our Sub-Zero repair in London page.
Sub-Zero error code list
The meanings below are taken from Sub-Zero’s own owner help pages (subzero-wolf.com/assistance). The same number can be shown differently on different series, so check which family your model belongs to.
Code | What Sub-Zero says it means | Models |
40 1 40 | Excessive run time, refrigerator / zone 1 | Classic (BI), Designer / Integrated, wine |
40 2 40 | Excessive run time, freezer (Classic) or zone 2 | Classic (BI), Integrated wine |
40 3 40 | Excessive run time, zone 3 | Designer / Integrated, wine |
40 / EC40 | Excessive freezer compressor run time | 600, 700, PRO 48 |
50 / EC50 | Excessive refrigerator compressor run time | 700, Designer / Integrated |
24 / EC24 | Defrost underheat | 600, 700 |
21 / EC21 | Defrost overheat | 600 |
EC30 | Ice maker shut off: water valve worked too many times | 600, 700 |
EE | Faulty temperature sensor (left freezer, right fridge) | 600, Classic, 700, PRO 48, 400 wine |
98 0 98 | Brownout: the mains voltage dropped | Classic (BI) |
15 1 01 | Refrigerator compressor relay stuck closed or electrical interference | Classic (BI) |
How a Sub-Zero shows an error code
600 and 700 Series (for example the 632, 642, 650 and 695): the word Service flashes between the temperature displays, and a code may appear as a number alternating with EC, such as EC40. A steady Service light means codes from an earlier fault are still stored.
Classic, formerly Built-In (BI-36, BI-48 and similar): a wrench icon lights or flashes, and codes appear in three parts, such as 40 1 40 or 98 0 98. A flashing wrench with the alarm chiming means a major error code has been logged.
Designer / Integrated (IT, IC, ID columns and drawers): three-part codes such as 40 1 40 and 40 3 40, where the middle number is the zone.
PRO 48: Service flashes on the outside display; behind the grille there is a service display that an engineer uses to read the fault history.
Newer connected models: errors also appear in the Sub-Zero Group Owner’s App, with a yellow triangle for a problem you can usually fix and a red triangle or Service Required when an engineer is needed.
What does Sub-Zero error code 40 1 40 mean?
According to Sub-Zero, error code 40 1 40 means excessive run time: the refrigerator (zone 1) compressor has been running for longer than it should. On Classic (Built-In) models, 40 2 40 is the same fault for the freezer, and on Designer / Integrated and wine models 40 2 40 and 40 3 40 refer to zones 2 and 3. Sub-Zero's advice is to switch the breaker off for 30 seconds, switch it back on and, if the code returns, book a service engineer. A long run time is a symptom, not a cause: the compressor keeps running because the cabinet is not reaching its set temperature. The usual reasons are a dirty condenser, a fan that has stopped, ice on the evaporator after a defrost fault, a door seal that leaks, or a refrigerant or compressor problem. Our guide to why a Sub-Zero fridge stops cooling properly covers these in more detail.
What does EC40 or error code 40 mean on a Sub-Zero?
On 600 Series, 700 Series and PRO 48 models, code 40 (shown as EC40, or 40 alternating with EC) means excessive freezer compressor run time. Sub-Zero lists a door left ajar, a sealed system problem, a fan problem or a temperature sensor problem as possible causes. If the temperatures are high, call an engineer; if they are close to normal, clean the condenser and clear the code. If you clear the code and it comes back within a day or two, the fault is still there and the freezer needs an engineer. See our Sub-Zero freezer repair page.
A real case: error 40 on a Sub-Zero PRO 48
In November 2026 LE Company engineers were called to a Sub-Zero PRO 48 in London whose freezer section had stopped working. The service display behind the grille showed two stored faults: error 40, long compressor run, and Error 91 4, which our engineer read as a fault in the lighting system.
The freezer compressor did not start in normal operation. With a separate starting device connected it started, and it passed a test with a speed controller, so the next step is to replace the compressor inverter and re-test, and to replace the compressor only if that does not cure it. Error 40 had been the first sign: the freezer was calling for cold that the compressor could no longer deliver.
Sub-Zero error code 24 and 21: defrost faults
Code 24 (EC24) means defrost underheat: the defrost heater did not warm the evaporator as expected. Code 21 (EC21) is the opposite, defrost overheat. Both are listed by Sub-Zero for 600 and 700 Series refrigerators. A defrost fault matters because the evaporator slowly blocks with ice, airflow stops and the cabinet warms up, which then often triggers a run-time code as well. In another case, a Sub-Zero drawer fridge kept tripping the breaker during defrost because the defrost heaters had an earth fault.
Sub-Zero error code 50
Code 50 (EC50) is the refrigerator-side twin of code 40: excessive refrigerator compressor run time. Sub-Zero lists it for 700 Series and Designer / Integrated models. The checks are the same: temperatures first, then the condenser, then an engineer if the code returns.
Why is the Service light flashing on my Sub-Zero?
On 600 and 700 Series models such as the 632, 642, 650 and 695, a flashing Service indicator means the control has detected a fault, most often excessive compressor run time, which can mean a cooling problem. A steady Service light means fault codes are still stored in the control. On Classic models a flashing wrench icon with the alarm chiming means a major error code has been logged. If Service flashes together with the ice indicator, Sub-Zero says the ice maker water valve has been energised for too long; switch the ice maker off and book a repair (see Sub-Zero ice maker repair).
What does EE mean on a Sub-Zero display?
EE means a faulty temperature sensor (thermistor). On 600 Series, Classic and PRO 48 models, EE on the left of the display refers to the freezer sensor and EE on the right to the refrigerator sensor. It is not something an owner can fix: the sensor has to be tested and replaced.
What about PP and other codes?
Sub-Zero does not publish a meaning for every code on its owner pages. We could not find an official meaning for PP, so we will not guess one here. If your Sub-Zero shows a code that is not in the table, take a photo of the display and the rating plate inside the cabinet, and send it to us with your enquiry: our engineers read the full fault history on site.
How do I reset a Sub-Zero error code?
Sub-Zero's general reset is to switch the unit off at the control panel, then switch the breaker off for 30 seconds and back on. On many models a code can also be cleared by holding the door-ajar (bell) key for 15 seconds once the fault is fixed. Only clear a code if the temperatures are recovering: the engineer needs the stored code to find the fault.
Sub-Zero also warns that on Designer and 700 Series models a kickplate fully covered by custom cabinetry can starve the unit of air and lead to a sealed system failure, so check that the grille is not blocked. Keeping the condenser clean is part of regular Sub-Zero maintenance, and it prevents many run-time codes before they appear.
When to call a Sub-Zero engineer
Call an engineer if a code comes back after a reset, if the temperatures are rising, if you see EE, or if the unit trips the electrics. Do not keep resetting it: every reset can hide the stored code the engineer needs. For what a repair usually costs, and whether an older unit is worth repairing, see our Sub-Zero repair cost guide.
Book a Sub-Zero repair in London
LE Company’s call-out is from £175 + VAT and includes the first 30 minutes on site, when the engineer reads the fault codes and finds the cause. The cost of the repair is agreed with you before any work starts, and we fit only original Sub-Zero parts. See our Sub-Zero repair in London page, read our frequently asked questions, or call +44 20 3603 7172, Monday to Saturday, 8am to 8pm.