Lennox E241 Error Code: Flame sensed out of sequence
Updated October 2026 · Sourced from Lennox documentation
🛑 Turn it off and call a licensed pro
The control still senses flame when it should not be there.
Is it safe to keep running? No. Turn it off and get it checked. Call a licensed HVAC technician right away. Do not use the furnace until it has been checked.
E241 at a glance
| Code / how it shows | Meaning | Applies to |
|---|---|---|
| E241 Shown as an E code on the 7-segment display of the integrated control | Flame sensed out of sequence | Lennox SL280UHVK two-stage variable-speed furnace (integrated control, 7-segment display) |
Check this first
Only steps a homeowner can do safely. Do not open electrical panels or the burner area.
- If you smell gas, leave the building and call your gas company from outside. Do not touch switches.
- Turn the furnace off at the thermostat.
🛑 Stop and call a licensed pro if
- Call a licensed HVAC technician right away. Do not use the furnace until it has been checked.
- You smell gas. Leave the house, do not touch switches, and call your gas utility from outside.
- Flame rollout, limit or pressure switch codes that come back after one reset.
- Anything involving the control board, gas valve, flame sensor, igniter or venting.
- A carbon monoxide alarm sounds. Get everyone outside and call 911 or the fire department.
Safe first steps for any Lennox code
- Count the LED flashes through the blower door window before you switch anything off. Cutting power can clear the code.
- Replace or clean the furnace air filter.
- Check the thermostat: correct mode, set above room temperature, and fresh batteries.
- Make sure the furnace power switch and breaker are on. If the furnace has locked out, turning the power off and back on once restarts it.
- Make sure the gas valve is in the ON position, following the lighting instructions on the furnace label only.
- On high-efficiency furnaces, look at the outside vent and intake pipes for snow, ice, leaves or nests (look only, do not take pipes apart).
Source: Lennox SL280UHVK Installation Instructions 508553-01 (01/2025), Ignition Control Diagnostic Codes, p.36. Codes are series-specific, so your unit's own manual is the final word. Reviewed October 2026.
Shaun Cain · Certified HVAC & Refrigeration Technician · Ask an HVAC technician
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