Lennox E241 Error Code

What does Lennox E241 mean?

E241 means the flame sensor is detecting a flame signal when no flame should be present — the gas valve is commanded closed but the IFC still reads flame current. This is a safety-critical condition indicating that gas may still be flowing through a leaking gas valve. The board logs E241, shuts off all outputs, and clears the alert only after the flame signal disappears.

Symptoms

• Furnace shuts down unexpectedly and E241 is displayed on the thermostat or control board.
• Flame sensor reads current after the gas valve should have closed.
• Smell of gas or persistent combustion odor after the furnace shuts down.
• Alert occurs at the end of a heat call when the gas valve de-energizes.

Common causes

• Leaking gas valve main seat allowing gas to continue flowing after the valve is de-energized.
• Flame sensor wiring shorted to ground or another circuit, producing a phantom flame signal.
• Faulty IFC board flame sensing circuit that holds a false positive signal.
• Residual flame from carbon deposits on the burner that continue to burn briefly after gas shutoff.

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Diagnostic steps

1. Shut off the gas supply immediately

   Turn off the manual gas shutoff valve upstream of the furnace. A leaking gas valve is a safety hazard — do not continue operating the furnace until the cause is confirmed.

2. Inspect the flame sensor wiring for shorts

   Check the flame sensor lead for contact with the furnace cabinet, burner assembly, or other conductors that could create a phantom flame signal. Correct any wiring fault found.

3. Test the gas valve for internal leakage

   With the furnace powered and the gas valve commanded closed, use a combustible gas detector or soapy water at the downstream side of the valve (with gas supply on) to check for seepage past the main seat.

4. Replace the gas valve if leakage is confirmed

   A leaking gas valve seat cannot be repaired in the field. Install the Lennox OEM replacement gas valve, verify all gas connections are leak-free, and restore operation.

5. Replace IFC board if gas valve and wiring check out

   If gas valve seating is confirmed tight and the flame sensor wiring is correct, the IFC board's flame sensing input circuit is producing a false signal. Replace the control board.

When to call a professional

E241 is a safety lockout that requires gas valve inspection and potentially gas valve replacement — work that involves breaking the gas line and verifying leak-free reassembly. This is a mandatory licensed-technician repair. Do not restore furnace operation until a qualified technician has confirmed the gas valve is not leaking and E241 does not return.