Boiler displays E2 and shuts down shortly after starting; burner may light briefly then go out.

Safety first: Turn off power and gas before working inside the boiler. Allow components to cool.

• Step 1 – Clean flame sensor: Remove the flame sensor and gently clean the metal rod with fine abrasive pad. Wipe off dust and reinstall, ensuring it is positioned correctly in the burner flame path.
• Step 2 – Inspect burner and orifices: Remove the burner assembly if accessible. Check for rust, debris, or spider webs in the burner ports and orifices. Clean with a soft brush and compressed air (do not enlarge orifices).
• Step 3 – Check ground and wiring: Verify that the flame sensor wire is intact and firmly connected to the control board. Confirm the boiler chassis ground connection is tight and free of corrosion.
• Step 4 – Verify gas pressure (pro only): Low manifold pressure can cause flame dropout. A licensed technician should measure inlet and manifold gas pressure at the gas valve using a manometer and adjust or correct supply issues.
• Step 5 – Reset and test: Restore power and gas, reset the control, and observe operation. If E2 persists, the control board or gas valve may require replacement.

Note: Flame sensing issues are often resolved by cleaning the sensor and ensuring a clean, stable burner flame.