Lennox SLP98UHV Error Code E 241: Flame Sensed Out of Sequence
What Does Code E 241 Mean?
Error code E241 on the Lennox SLP98UHV indicates that the flame sensor is detecting a flame signal when the gas valve should be off and no flame should be present. This is a potentially dangerous condition that suggests gas may be flowing when it should not be.
The most likely cause is a gas valve that is leaking or stuck in the open position. When the gas valve fails to fully close, gas continues flowing to the burners, which can ignite from residual heat or other ignition sources. The control board detects this through the flame sensor and shuts down the system.
In rare cases, a false reading from the flame sensing circuit (such as a short in the flame sensor wiring or moisture on the sensor) can trigger this code without an actual flame. However, because the consequences of a true gas leak are severe, this code should always be treated as a genuine safety concern until a technician can verify otherwise.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Gas valve leaking or stuck open, allowing gas to flow when it should be off | Most common | ✗ Call a pro → |
When to Call a Professional
Contact a licensed HVAC technician if:
- This code requires immediate professional attention — turn off the gas supply right away
- You smell gas near the furnace at any time
- The furnace has shut down and is displaying E241
✓ Verified against manufacturer service manual — March 2026