Lennox Furnace Error Code E 290

E 290 on a Lennox furnace indicates an ignitor circuit fault, meaning the control board has detected that the hot surface ignitor or its associated wiring and triggering circuitry is not functioning correctly. The furnace cannot complete a successful ignition sequence, so it enters a 1-hour soft lockout as a safety measure. The code clears automatically once a stable flame has been proven after the issue is resolved.

The furnace is designed to lock out when it cannot confirm successful ignition, which prevents unburned gas from accumulating in the heat exchanger or home. The soft lockout triggered by E 290 is a protective response, not a sign of an active gas leak. However, you should not repeatedly attempt to force restarts without diagnosing the root cause, and if you smell gas at any point, leave the home and contact your gas utility immediately.

E 290 triggers a 1-hour soft lockout that will clear on its own once the furnace proves a stable flame during a successful ignition cycle. You can attempt a manual reset by cycling power to the furnace, but if the ignitor or wiring fault is still present, the code will return as soon as the furnace tries to ignite again. A permanent resolution requires identifying and correcting the underlying ignitor circuit problem.

A knowledgeable DIYer can start by measuring the resistance of the hot surface ignitor with a multimeter. If the reading falls outside the 39-70 ohm range or shows an open circuit, the ignitor needs to be replaced, which is a manageable repair for someone comfortable working with furnace components. However, if the ignitor tests good and the fault persists, diagnosing wiring harness issues or a failed control board component is best handled by a qualified HVAC technician.

If the hot surface ignitor is the problem, parts typically cost between $20 and $80 depending on the specific ignitor, and a technician's labor to diagnose and replace it generally adds another $80 to $200. If the fault lies in the control board, repair costs can range from $250 to $600 or more for parts and labor. Getting a diagnostic estimate from a licensed HVAC technician is the best way to determine the actual cost for your specific situation.