York Furnace 3 Green Flashes (YP9C Modulating)
StatusShown as: Three green flashes after holding the LAST ERROR button more than five seconds
Indicator for 'Error codes cleared from memory'. Not a fault.
Manual wording: “Three Green Flashes - Indicator for "Error codes cleared from memory".”
Documented for: YP9C, YPLC modulating furnaces
Likely causes, most common first
- The stored fault history was cleared with the LAST ERROR button
When to call a technician
Not a fault, but clearing the history erases what a technician needs to chase an intermittent problem - leave it alone before a service visit.
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