Coleman Furnace 6 Red Flashes (CP9C Echelon Modulating)
Soft lockoutShown as: Six red flashes, two-second pause, repeating
Gas valve communication error. The modulating gas valve and the control board have lost their data link, so the furnace cannot modulate or fire.
Manual wording: “Six Red Flashes - Gas valve communication error.”
Documented for: CP9C Echelon modulating furnaces
Likely causes, most common first
- Loss of communication between the control board and the modulating gas valve
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
Modulating gas valve communication faults are a technician job - the valve, its harness and the board all have to be checked.
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