Lennox · Furnace error code

LED1 fast flash + LED2 fast flash (together)Normal heat operation

Single source Power off, standard tools

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Related diagnostic guides

Guide · Furnace

Burning smell when the heat first comes on

Dust settled on the heat exchanger or electric heat strips burns off at the first firing and fades within a few hours. A smell that lingers, or smells like plastic, rubber, hot wiring or gas, is not normal and needs diagnosis.

4 steps ~30 mineasy

Guide · Furnace

Furnace runs no heat (blower only or nothing)

Start with the board LED code, then work the call path: thermostat, 24 V, safeties, inducer, ignition, flame proving. Most no-heat calls end at a filter, a flame sensor, a pressure switch issue or gas being off.

5 steps ~45 minmoderate

Guide · Furnace

Limit trips / overheating (airflow)

The limit protects the heat exchanger from overheating. The fix is almost always airflow: filter, blower, ducts. Rollout switch trips are different and must be referred.

4 steps ~45 minmoderate

More Lennox furnace codes

Lennox · Furnace

E223

Low pressure switch failed open

Cross-checked High-voltage / caution

Lennox · Furnace

E228

Pressure switch calibration unsuccessful

Single source High-voltage / caution

Lennox · Furnace

E241

Flame sensed out of sequence

Cross-checked Licensed pro only

Lennox · Furnace

E250

Limit switch circuit open

Cross-checked High-voltage / caution

Lennox · Furnace

E290

Igniter circuit fault

Cross-checked High-voltage / caution

Lennox · Furnace

E292

Indoor blower cannot start

Cross-checked High-voltage / caution