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Error code reference

York Furnace Error Code 2 Flash

Low fire pressure switch (1LP) contacts are stuck in the closed position; control must first see an open…

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Low fire pressure switch (1LP) contacts are stuck in the closed position; control must first see an open circuit then a closed circuit to ensure safety.

First step from the service manual

Check for incorrect wiring (jumper left in place across the switch) or a failed switch.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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What 2 Flash means on a York furnace

The 2 Flash error code on a York furnace indicates that the control board has detected the low fire pressure switch (1LP) contacts in a closed position at a point in the startup sequence when they should be open. The furnace control performs a critical safety check during ignition: it must first confirm the pressure switch is open (no pressure detected), then verify it closes (pressure confirmed) once the inducer motor runs. If the control sees the switch already closed before the inducer starts, it cannot confirm this open-to-closed transition, and it locks out as a safety precaution.

The low fire pressure switch is a normally open switch that monitors negative pressure (draft) inside the inducer assembly. It closes when the inducer fan generates sufficient airflow and pressure differential. A stuck-closed or shorted switch bypasses this verification step, which is why the control board treats this condition as a fault rather than allowing the heating cycle to proceed.

The most common causes are an installation or service error where a jumper wire has been left across the 1LP switch terminals, or a failed pressure switch whose internal diaphragm or contacts have mechanically stuck in the closed position. A shorted or damaged wire in the switch circuit can also produce the same symptom. Because this switch is part of the ignition safety sequence, the control board will not allow the furnace to fire until the fault is resolved and a valid open-then-closed transition can be observed.

Source: manufacturer service documentation.

Common causes of 2 Flash

  1. 01

    Jumper wire left across switch terminals

    Wiring / connection

    During troubleshooting or installation, a technician may have placed a jumper across the 1LP pressure switch terminals and not removed it. This directly shorts the switch contacts and makes the control board see a permanently closed circuit.

  2. 02

    Failed low fire pressure switch (1LP)

    Part replacement

    The diaphragm or internal contacts of the pressure switch can fail in the closed position. Disconnecting the switch wires and checking continuity across the switch terminals will confirm whether the switch is stuck closed.

  3. 03

    Shorted wiring in the pressure switch circuit

    Wiring / connection

    A pinched, damaged, or incorrectly routed wire in the 1LP circuit can create a short that mimics a closed switch. Inspecting the wiring harness from the switch to the control board for insulation damage or contact with grounded metal is the key diagnostic step.

  4. 04

    Incorrect wiring at the control board or switch terminals

    Wiring / connection

    A miswired connection that ties the 1LP signal wire to a voltage source or another circuit can hold the input artificially closed. Verifying the wiring against the furnace wiring diagram will reveal this condition.

See the test procedure for each cause

Frequently asked questions about 2 Flash

What does 2 Flash mean on a York furnace?
A 2 Flash error code on a York furnace means the low fire pressure switch (1LP) contacts are detected in the closed position before the inducer motor has started. The control board requires seeing the switch open first, then close, to confirm safe draft conditions. Because this sequence cannot be completed, the furnace locks out and displays the 2 Flash fault. The problem is typically a jumper left on the switch terminals or a failed switch.
Can I fix a 2 Flash error on my York furnace myself?
If you have basic electrical knowledge, you can check whether a jumper wire was left across the pressure switch terminals and remove it, which may resolve the fault immediately. Beyond that, testing the pressure switch with a multimeter for stuck-closed contacts is a straightforward check, but replacing gas furnace components does carry safety risks. If you are not comfortable working inside the furnace, a licensed HVAC technician should perform the diagnosis and repair.
Is a 2 Flash error on a York furnace a safety hazard?
The 2 Flash fault is the furnace protecting itself rather than an active danger in the home. The control board prevents the burners from firing until the pressure switch issue is resolved, so there is no risk of gas buildup or combustion with the furnace locked out. However, the underlying issue must be corrected before the furnace will operate, and bypassing or ignoring the fault is not safe.
Will resetting my York furnace clear the 2 Flash error code?
Resetting the furnace by cycling power will allow it to attempt startup again, but if the root cause is not corrected, the 2 Flash code will return during the next startup sequence. The control board runs the pressure switch check on every startup attempt, so the fault will persist until the shorted wiring, jumper, or failed switch is addressed.
How much does it cost to repair a 2 Flash error on a York furnace?
If the cause is a jumper wire left in place, the fix may cost nothing beyond a service call fee, typically in the range of $75 to $150. If the low fire pressure switch needs replacement, parts and labor combined generally fall in the range of $100 to $300 depending on your location and the service provider. Wiring repairs can vary more widely depending on the extent of the damage found.

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