Quick answer
Lennox furnace error code E270 is a soft lockout: the furnace exceeded its maximum number of retries with no flame current sensed. There is no heat while it is locked out, and the code clears only when a heat call finishes successfully. Confirm the gas supply to the furnace is on and cycle power once. Repeated lockouts need service, not more resets.
A Lennox furnace showing error code E270 has stopped trying to light, and that is exactly what the code means: soft lockout. The control exceeded its maximum number of retries and sensed no flame current. Lennox defines it that way in the ignition control diagnostic code table for the EL296DFV. Model differences are real, so treat the chart on the label inside the furnace panel as the final reference.
What a soft lockout means for your heat
There is no heat while the furnace is locked out. The control has stopped opening the gas valve because repeated attempts produced no proven flame, which is the correct response. The code clears only when a heat call finishes successfully, so a reset by itself does not erase it; a completed heating cycle does.
Confirm the gas supply, then cycle power once
- Try another gas appliance. If the range or water heater has no gas either, the supply to the house is off and the furnace is not the problem.
- Look at the shut-off valve on the gas line at the furnace. The handle runs parallel to the pipe when the valve is open.
- On propane, read the tank gauge. Rural homes around Carlisle, Lowville and rural Flamborough heat with propane where gas mains do not reach, and a tank that has run out means no gas at the burners.
- Switch the furnace power off, wait 30 seconds, switch it on, and let it attempt one full start.
- If you smell gas at any step, stop, go outside and call your gas utility or 911.
The three checks in Lennox's table: gas flow, ignitor, flame-sensor current
Lennox's own table reduces E270 to three questions. Is gas reaching the burners? Is the ignitor lighting the burner? Is the flame sensor passing current to the control once the burner is lit?
What you noticed during the retries helps answer them. An ignitor glowing with no burner flame points at gas flow. Burners that lit briefly and went out point at the sensor or the ground. The causes, most likely first:
- Gas not reaching the burners: a closed valve, an interrupted supply, or a gas valve that is not opening.
- An ignitor that is not lighting the burner because it is cracked or weak.
- A dirty or failed flame sensor. The burners light and the control still sees no flame current, so it closes the gas valve and counts a failed try.
- A poor unit ground. Flame current needs a solid path back through the cabinet, and a corroded or loose ground breaks it.
Two related pages go deeper on the middle of that list: why a furnace igniter glows but the burners do not light and what a furnace flame sensor costs.
Why resetting E270 over and over is the wrong move
Each reset gives the furnace a fresh set of retries without changing the reason they fail. If the fault is a dirty sensor, the furnace may run for one cycle and lock out again that night. If the fault is on the gas side, nothing changes at all. One reset after confirming the gas supply is a test; a habit of resets is a furnace that needs service.
A technician measures the flame-sensor current with a meter, tests the ignitor, and confirms gas pressure at the valve. Those three readings identify the part instead of guessing at it. Gas-side work in Ontario requires a TSSA gas licence.
What an E270 repair costs
- Cleaning or replacing the flame sensor: $150–$300
- Hot surface ignitor: $200–$450
- Gas valve: $500–$1,000
- Control board, when the readings point there: $500–$1,200
- Diagnostic visit: $90–$150, credited when you approve the repair
Most furnace repairs fall in the $150–$800 band, and the pricing page lists the figures by part. A flame sensor that only needs cleaning is the least expensive outcome on this list, which is one more reason to have the readings taken before anything is swapped. You get the price in writing before any part is replaced.
ZK Mechanical services Lennox furnaces across Burlington, Oakville, Milton, Hamilton and Mississauga, and the 24/7 emergency line takes no-heat calls with no after-hours surcharge. If E270 is back after one reset, book furnace repair or contact us with the code and the furnace model. The Lennox furnace error code guide lists the other codes you may see alongside it.