Lennox E290 Error Code

What does Lennox E290 mean?

E290 indicates a fault in the hot surface ignitor circuit — either the ignitor element itself has failed open or the triggering circuitry on the IFC board cannot properly energize the ignitor. The board monitors the ignitor circuit before and during the warm-up period; an open or out-of-range resistance reading causes E290. The furnace enters a soft lockout for approximately one hour before allowing another attempt.

Symptoms

• Furnace inducer runs but no glow is visible at the ignitor during the trial for ignition.
• E290 alert on thermostat or control board; no heat produced.
• Furnace may attempt ignition and immediately abort upon detecting the ignitor fault.
• Alert returns on every call for heat if the ignitor is physically broken.

Common causes

• Open or cracked silicon nitride ignitor element — resistance reads OL instead of 39–70 ohms.
• Failed ignitor triggering relay or triac on the IFC board unable to supply ignitor power.
• Open circuit in the ignitor wiring harness between the board and the ignitor connector.
• Ignitor that has reached end of life after repeated thermal cycling.

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Diagnostic steps

1. Power down and measure ignitor resistance

   Turn off the furnace disconnect. Disconnect the ignitor harness and measure resistance across the ignitor terminals. A reading of 39–70 ohms is acceptable; OL (open) confirms a failed element.

2. Inspect ignitor for visible cracks

   Remove the ignitor from the burner assembly and visually inspect the silicon nitride element. Fractures or carbon tracking on the element surface confirm physical failure.

3. Check ignitor wiring harness continuity

   With the ignitor disconnected, measure continuity from each pin of the IFC ignitor output connector through to the ignitor connector. Open continuity on any conductor indicates a harness fault — repair or replace the harness.

4. Verify IFC board ignitor output voltage

   With a known-good ignitor installed and the furnace powered, measure voltage at the ignitor terminals during the ignitor warm-up period. Expected output is 120V AC; no voltage indicates a failed IFC triggering circuit.

5. Install replacement ignitor

   Handle the new ignitor only at the ceramic base. Align the element correctly in the burner port and torque the mounting screw per the IOM. Run a test ignition cycle to confirm the fault clears.

When to call a professional

If the ignitor resistance is within spec and 120V is reaching the ignitor connector but E290 persists, the IFC board's ignitor monitoring circuit is faulty. Diagnosing board-level ignitor sensing circuits requires a factory service tool. A licensed technician can differentiate a board fault from an intermittent ignitor fault and make the correct repair.