York Furnace 2 Red Flashes (YP9C Modulating)
Soft lockoutShown as: Two red flashes, two-second pause, repeating
The pressure switch is closed while inducer pressure is below the switch setpoint - the switch is closed when it should be open, so the control will not start.
Manual wording: “Two Red Flashes - Pressure switch closed with inducer pressure below pressure switch setpoint (switch is closed when it should be open). Check pressure switch and pressure transducer.”
Documented for: YP9C, YPLC modulating furnaces
Likely causes, most common first
- Faulty pressure switch stuck closed
- Faulty pressure transducer
What you can safely check yourself
- Turn the furnace off at the service switch for a minute and back on once to see whether the code clears
When to call a technician
A stuck pressure switch is a safety interlock failure. It must be tested and replaced by a technician - never jumper it.
A York furnace throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Source
- Installation Manual - Modulating ECM Residential Gas Furnace with ECM Motor, Models YP9C*C / TP9C*C / CP9C*C / LP9C*C (Up to 98% Modulating Multi-position), 1083292-UIM-A-0114 (Johnson Controls Unitary Products (York), YP9C*C (York Affinity modulating), and the identical TP9C / CP9C / LP9C chassis) · checked 2026-08-25