Coleman Furnace: 12 Flashes
Code 12 red flashes (CP9C Echelon modulating): The model ID plug is not present or not connected properly
WarningShown as: Twelve red flashes, two-second pause, repeating
The model ID plug is not present or not connected properly.
Manual wording: “Twelve Red Flashes - ID plug is not present or not connected properly, check for loose plug or loose wires in plug.”
Documented for: CP9C Echelon modulating furnaces
Likely causes, most common first
- Loose ID plug
- Loose wires in the ID plug
- Missing ID plug
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
Have a technician confirm the correct ID plug is fitted and seated - the wrong plug makes the furnace fire at the wrong rate.
A Coleman furnace throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Source
- Installation Manual - Residential Gas Furnace with ECM Motor, Models TP9C*C, YP9C*C, CP9C*C, LP9C*C (Up to 98% Modulating Multi-position), 681292-UIM-B-1211 (Johnson Controls Unitary Products (Coleman), CP9C*C Coleman Echelon modulating gas furnace (manual also covers the identical TP9C, YP9C and LP9C chassis)) · checked 2026-08-25
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