Carrier Furnace Code 45.2
Safety faultShown as: Major code 45 on the LED (4 short, 5 long); 45.2 on the 3-digit display
Control failure - the gas valve relay on the control board will not close.
Manual wording: “45.2 CONTROL FAILURE - gas valve relay will not close.”
Documented for: 58SC0B/58SC1B
Likely causes, most common first
- Failed gas valve relay on the control board
What you can safely check yourself
- Turn the furnace off at the service switch and leave it off until a technician arrives
When to call a technician
A gas valve relay that will not close means the board can no longer control gas flow reliably. Shut the furnace off and call a technician; the manual's fix is to replace the control.
A Carrier furnace throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Source
- Installation, Start-Up, Operating and Service and Maintenance Instructions - 58SC0B/58SC1B (Carrier, 58SC0B/58SC1B single-stage condensing gas furnace with 3-digit status display) · checked 2026-08-25