Furnace locks out with E2 shortly after ignition, flame appears briefly then goes out

Safety first: Turn off power and fuel supply. Combustion components can be hot; allow cooling time.

Steps:

• Clean flame sensor: Locate the Danfoss flame sensor (ionization electrode or photocell) at the burner head. Remove it carefully and clean the sensing surface with fine steel wool or a non-abrasive pad. Do not scratch or bend the rod.
• Check sensor wiring and ground: Inspect the flame sensor lead for cracks, burns, or loose connectors at the Danfoss control module. Ensure the burner chassis is firmly grounded to the furnace frame and earth ground.
• Verify combustion air and flue: Check that the combustion air intake and flue gas outlet are not blocked by snow, leaves, nests, or soot. Clear any obstructions and ensure terminal screens are clean.
• Check fuel pressure (visual/basic): For oil systems with a Danfoss oil pump, inspect the oil filter and replace if dirty. For gas, ensure the gas supply valve is fully open. Detailed pressure checks require a manometer or gauge and should be done by a technician.
• Reset and observe: Restore power and fuel, reset the control, and watch the flame through the inspection port. If the flame is unstable, noisy, or lifting off the burner head, stop and call a professional for combustion adjustment.