Lennox Furnace Error Code E260

E260 indicates a soft lockout condition caused by the furnace exceeding the maximum number of ignition retry attempts without ever detecting a flame signal at the flame sensor. The control board runs through a set number of trials for ignition, and if flame current is never confirmed during any of those attempts, it stops and logs E260. This protects the system from repeatedly releasing unlit gas. The three most common culprits are a dirty flame sensor, interrupted gas supply, or a failing ignitor.

E260 itself reflects the control board working correctly by stopping ignition attempts after repeated failures, which prevents the unsafe accumulation of unburned gas. The lockout is a protective response, not a sign that something dangerous has already occurred. That said, if you smell gas near the furnace at any point, leave the building immediately and contact your gas utility. A faulty gas valve that sticks open is a rare but serious condition that requires professional evaluation.

The most reliable way to test the flame sensor is to connect a microamp meter in series with the sensor lead during an active ignition cycle. If the burner lights but the current reading is near zero or below the threshold the control board requires, the sensor is not signaling properly. In many cases, removing the sensor rod and gently cleaning the tip with fine steel wool or emery cloth to remove oxide buildup is enough to restore normal current flow. If the furnace does not light at all during the trial, the sensor is not the starting point and gas supply or ignitor function should be checked first.

Because E260 is a soft lockout, the furnace may reset automatically after a waiting period or after the thermostat call for heat is cycled off and back on. However, resetting without addressing the root cause will result in the furnace attempting ignition again and returning to lockout if the problem persists. A reset is useful for confirming the fault is repeatable and for observing the ignition sequence, but it is not a repair. The underlying issue with gas flow, the ignitor, or the flame sensor must be resolved.

Repair costs depend entirely on the failed component. Cleaning a dirty flame sensor is an inexpensive service call, generally in the range of $80 to $150 for labor alone if no parts are needed. Replacing a hot surface ignitor typically costs $150 to $300 including parts and labor. A gas valve replacement is more involved and can range from $300 to $600 or more depending on the model and labor rates in your area. Diagnosing the specific cause before authorizing repairs is the best way to understand the cost.