Lennox SLP98UHV Error Code E 270: Soft Lockout - No Flame Sensed
What Does Code E 270 Mean?
Error code E270 on the Lennox SLP98UHV indicates a soft lockout after exceeding the maximum number of ignition retries with no flame current sensed. The furnace tried to light multiple times but the flame sensor never detected a flame. The lockout clears when a subsequent heat call finishes successfully.
During each ignition attempt, the control board energizes the hot surface igniter, opens the gas valve, and waits for the flame sensor to detect a flame. If no flame is sensed within the allowed time window, the gas valve closes and the system retries. After exhausting its retry limit, the furnace enters soft lockout.
There are two main categories of causes. First, the burners may be lighting but the flame sensor is too dirty to detect the flame — this is the most common cause. Second, the burners may not be lighting at all, which points to a gas supply issue (closed manual gas valve, empty propane tank, or utility shutoff), a failed hot surface igniter, or a gas valve problem. If you can see through the sight glass that the burners light briefly before the gas shuts off, the flame sensor is the most likely culprit.
Common Causes
When to Call a Professional
Contact a licensed HVAC technician if:
- E270 returns after cleaning the flame sensor and verifying gas supply
- The burners do not ignite at all (no flame visible through the sight glass)
- The igniter does not glow during the ignition sequence
- Other gas appliances in your home are working fine but the furnace will not light
- You smell gas near the furnace but the burners will not ignite
✓ Verified against manufacturer service manual — March 2026