York furnace — York YP9C modulating condensing gas furnaces documented in the York installation manual Error Codes Directory
Complete diagnostic reference for York furnace — York YP9C modulating condensing gas furnaces documented in the York installation manual fault codes. Each code includes official root causes, safety precautions, and affected replacement components.
York YP9C two red flashes: the draft proving circuit did not behave
Two red flashes on a York YP9C control points at the draft proving circuit: the pressure switch has not reached the state the control expects for the stage of the sequence it is in. The count identifies the circuit, not the component, so the inducer, the vent path, the condensate arrangement, and the switch itself are all inside the reading. Applies to: York YP9C modulating condensing gas furnaces documented in the York installation manual This applies to the York YP9C modulating condensing furnace as documented in its installation manual. York uses different flash tables on other furnace lines, and a modulating furnace proves draft across more than one firing rate, which changes what a fault at a particular stage implies compared with a single-stage appliance. Owner-safe checks: Count the flashes carefully through the sight glass, keeping the blower door closed so control power is not interrupted. | Check the outdoor vent and intake terminations from ground level for snow, ice, nests, or plant growth without climbing or probing. | Note whether ignition is ever attempted and whether the fault is linked to a change in firing rate. Qualified technician: Measuring draft pressure, testing the inducer, clearing condensate traps, and verifying switch operation at each firing rate are licensed gas-furnace tasks. | Any indoor smell of combustion products, or a carbon monoxide alarm, means leaving the appliance off, getting fresh air into the space, and calling the gas emergency number before anything else.
York YP9C five red flashes: flame where the control did not ask for it
Five red flashes on a York YP9C control reports flame present at a time the control did not command it. That is a statement about the gas train rather than about ignition performance, so the furnace should be taken out of use and handed to a licensed engineer rather than reset and observed. Applies to: York YP9C modulating condensing gas furnaces documented in the York installation manual The flash table referenced here is the one published for the York YP9C modulating condensing furnace. York assigns flash counts differently across its furnace lines, and equipment from related brands on similar control platforms carries its own table, so the model on the rating plate governs. Owner-safe checks: Check for any smell of gas first, and if one is present leave the property and call the gas emergency number from outside before anything else. | Isolate the appliance using the service switch fitted beside it, which ends the cycling without touching anything inside the cabinet. | Write down whether continued warmth or burner activity was observed, and at what point in the cycle the flashes appear. Qualified technician: Gas valve testing, burner inspection, and flame sensing circuit measurement on a modulating condensing furnace are licensed gas engineering tasks. | Do not restore the furnace to service to see whether the code returns. A repeat cycle is the risk this code is warning about.