Lennox furnace E270: Soft lockout — retries exceeded, no flame current sensed
E270 means the furnace used up its ignition retries and never sensed any flame current at all. It is the lockout for a furnace that is not lighting, as opposed to one that lights and loses the flame.
Applies to: Lennox gas furnaces with a seven-segment diagnostic display on the control board, such as the ML193UHEK, per installation instructions 508565-01.
What it means
Lennox splits its soft lockouts by what actually ended the sequence, which makes them far more useful than a generic lockout code. E270 is the retry family: the furnace attempted ignition the maximum number of times and no flame current was sensed on any of them. No flame current at all is a different situation from a weak signal. It means either nothing lit, or something lit and the sensing circuit could not see it even slightly. Lennox's steps follow that split — check for proper gas flow, confirm the ignitor is lighting the burner, and check the flame sensor current. The first two ask whether there was a flame; the third asks whether it could have been detected.
Most common causes
- No gas reaching the burners — a closed manual valve, an interrupted supply, or recent work on the gas line.
- An ignitor that is not lighting the burner, whether failed or out of position.
- A gas valve not opening when energised.
- A flame sensor so heavily coated, cracked or mispositioned that it reads nothing.
- A poor chassis ground or reversed line polarity, which prevents rectification entirely.
How to diagnose it
- Confirm the gas is on, including any manual valve at the furnace and at the meter.
- Note whether the burners light at all before shutdown. That single observation splits this code in half.
- Note whether other gas appliances in the house are working, which separates a furnace fault from a supply problem.
- The rest is inside the burner compartment and belongs to a technician.
How to fix it
- Technician work beyond confirming the gas supply.
- Lennox notes the lockout clears when a heat call finishes successfully, so the furnace will retry on its own.
- Stop resetting it repeatedly. Each attempt puts unburnt gas into the heat exchanger before the trial fails.
- Ground and polarity are worth confirming before parts are replaced.
Notes
The difference between E270 and E273 is the difference between never lighting and lighting then losing flame. Same lockout, opposite repairs.
Related
- E273 — Soft lockout — recycles exceeded after flame failure
- E290 — Ignitor circuit fault — failed ignitor or triggering circuit
All codes for this manufacturer
Lennox furnace alert codes — every code, with what differs between models.
What the fix costs
“No flame current sensed” splits the bill three ways, and Lennox's checklist walks them in rough price order. If the ignitor is not lighting the burner, the ignitor guide covers it: $150–350 installed, part alone $20–60 universal silicon nitride. If gas flow is the failure — supply valve, regulator, or the gas valve itself — the valve end of that is $300–900 and strictly professional. And if the burner lights but the control senses nothing at all, the flame-sense circuit is implicated beyond a mere dirty rod, which is where the ground and wiring checks earn their diagnostic time. The code's clearing condition — a heat call finishing successfully — costs nothing but tells you something: an E270 that stopped appearing after a warm afternoon has not been repaired, only interrupted.
DIY or call a pro
One observation through the closed sight glass, if your burner door has one, sorts this fault's whole first branch: during an attempt, does the ignitor glow orange? A glow followed by no flame moves suspicion to gas supply; no glow at all points at the ignitor or its circuit. That is watching, not touching — the door stays on, the hands stay out, and it is the single most useful sentence you can give the technician. The other homeowner check is embarrassingly upstream: confirm the manual gas shutoff near the furnace and at the meter were not closed by recent work elsewhere in the house, a genuinely common cause of a furnace that cranks and never lights. Beyond those, the ignition train and the retry cycle are professional ground, and the retry allowance has already been spent — repeated resets are re-running a failed experiment with gas.
The same fault on other brands
Retries-exhausted is coded in nine families; the seven-segment peers are the closest cousins to this one. Goodman's E0 is lockout after failed ignition attempts, the legacy Goodman/York 7 red flashes adds the same one-hour timing Lennox uses, and ICP's 6+1 flash specifies failure within four trials — different counts, identical conclusion. The igniter codes hub and this site's lockout pages map the family; what E270 adds over most is the explicit “no flame current” qualifier that rules the weak-signal explanations out.
What this looks like
From the outside, this usually shows up as the furnace turns over but never lights — that walkthrough covers what to check in order, and when it stops being a homeowner job.