Lennox HVAC Error Code 2 Flashes

The 2 Flashes code on a Lennox HVAC system signals an ignition lockout, meaning the furnace tried to ignite the burner but could not detect or sustain a flame within the allotted trial period. The control board shuts down all ignition activity as a safety measure to prevent unburned gas accumulation. The system will not attempt further ignition cycles until it is manually reset.

The lockout itself is a safety response designed to prevent hazardous conditions. The system stops attempting ignition precisely to avoid unburned gas from accumulating. However, repeated lockouts can indicate a gas supply or combustion problem that should be diagnosed promptly, and it is advisable to contact a qualified HVAC technician if the cause is not immediately apparent.

Repair costs vary depending on the failed component. Flame sensor cleaning is often a low-cost service call item, while a replacement flame sensor or igniter typically ranges from around $100 to $300 parts and labor combined. A faulty gas valve is more involved and can range from $300 to $700 or more depending on the model and labor rates in your area.

Start by resetting the unit to clear the lockout, then observe the next ignition attempt carefully. Check that the gas supply valve is fully open, inspect the flame sensor for oxidation or buildup, and verify the igniter glows bright orange during startup. If the lockout recurs, the flame sensor, igniter, gas valve, or inducer system will need further testing to isolate the specific component causing the fault.

Cycling power at the disconnect switch or thermostat will reset the lockout and allow the control board to attempt ignition again. However, if the underlying cause such as a dirty flame sensor, weak igniter, or gas pressure issue is not corrected, the system will repeat the ignition trials and return to lockout. A reset alone is not a repair.