Carrier Furnace Code 45.3
Soft lockoutShown as: Major code 45 on the LED (4 short, 5 long); 45.3 on the 3-digit display
Control failure - EEPROM memory issue on the control board.
Manual wording: “45.3 CONTROL FAILURE - EEPROM memory issue.”
Documented for: 58SC0B/58SC1B
Likely causes, most common first
- Corrupted or failed memory on the control board
What you can safely check yourself
- Turn the furnace off at the service switch for a minute and back on once
When to call a technician
If the code repeats after cycling power, the manual says to replace the control board.
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