What should I check first when my Lennox furnace shows an error?

Replace the filter, confirm power at the furnace switch and breaker, open all vents, clear intake/exhaust on high-efficiency models, then reboot (power off 60 seconds, back on). If the code returns—especially gas, limit, rollout, or repeated lockouts—stop and book service.

Is Error Code E 223 dangerous?

E 223 indicates a lockout related to the rollout circuit opening. Turn the system off and have a licensed technician inspect burners, gas pressure, and venting to rule out flame rollout and hazards.

How do I fix Error Code E 292 (restricted airflow)?

Start with a new filter and ensure all vents and returns are open. If airflow remains weak, ducts may be blocked or the blower misaligned. Schedule a professional to measure static pressure and correct airflow.

What is Error Code E 270 (flame not detected)?

No flame was detected during ignition. Clean or replace the flame sensor and check the igniter. If the code returns, a professional should check flame current, gas pressure, and burner alignment.

What does Error Code E 275 (flame detected out of sequence) mean?

Flame is sensed when it shouldn’t be. Inspect the burner assembly for debris or misalignment. A technician should check for gas valve leakage and verify sensor wiring and control logic.

What is Error Code E 131 (unresponsive blower motor)?

The blower isn’t responding—seized bearings, a stuck wheel, or a failed motor/ECM. Power down, clear obstructions, try spinning the wheel. If still unresponsive, a technician can confirm motor versus control failure.

Should I keep resetting to clear a furnace code?

One restart after filter and vent checks may be fine. Do not keep resetting codes involving limit, rollout, gas valve, or recurring lockouts—book furnace repair Toronto for a safe, lasting fix.

How do I prevent future error codes?

Replace filters on schedule, keep returns clear, book annual maintenance to clean burners and verify temperature rise, inspect vent terminations, and ensure your thermostat supports the furnace’s staging and blower profiles.

Lennox Furnace Error Codes Toronto – What They Mean

Q: What does Lennox Error Code E 105 mean?

E 105 signals a device communication problem on the system bus. Reseat low-voltage wiring at the control board and thermostat, inspect the harness, and if it persists, have a technician test the bus and control board.

Q: What does Error Code E 201 indicate?

E 201 usually points to an outdoor air temperature sensor failure or disconnection in communicating systems. Inspect connections and replace the sensor if faulty.

Q: What does Error Code E 240 (limit switch open) mean?

The furnace is overheating, typically due to poor airflow. Replace the filter, open vents, and clear returns. If it repeats, a technician should verify temperature rise, blower settings, duct static, and the limit switch itself.

For Saving
Sep 22
5 min read

Introduction

Blinking lights or an “E-code” on your Lennox? This Toronto-ready cheat sheet translates the most common furnace errors into plain English—what they mean, the safe fixes you can try, and when to stop and call a licensed tech. Start with filter/power/vent checks, then follow our pro triage for flame, limit, rollout, and airflow faults. If the code keeps coming back, we’ll step in with fast diagnostics and clean repairs across the GTA. Even searches like furnace repair Toronto end up here for a reason.

Read This First (Safety + Fast Wins)

Smell gas, see soot/rollout, hear arcing? Power down and call a pro—now.
Five quick checks before service:
1. Replace the filter (correct size/MERV).
2. Confirm power (furnace switch on, breaker not tripped).
3. Open all vents and clear return grilles.
4. Clear intake/exhaust (snow, lint, leaves).
5. Reboot: thermostat OFF → cut power 60s → restore → HEAT. Note the code if it returns.

Lennox Error Codes — Pro Triage (Code • Explanation • Solution)

Code	Explanation	Solution
E 105	System bus communication fault (controls/thermostat not “talking”).	Power-cycle, reseat low-voltage harness, inspect for damaged conductors; pro to test bus/board if it persists.
E 110	Low line voltage detected.	Check breaker/shared circuits; verify voltage with a multimeter. Persistent low voltage: electrician/HVAC tech.
E 125	Gas valve miswire/relay fault.	Don’t keep resetting. Verify wiring/polarity; tech to test coil/relay and replace if needed.
E 131	Blower motor unresponsive (stuck wheel, seized bearings, failed ECM).	Kill power, clear obstructions, spin wheel by hand. If dead, tech to test ECM/windings and replace motor as required.
E 201	Outdoor air temperature sensor failure (communicating systems).	Inspect connections; replace sensor if faulty.
E 223	Low pressure switch open (draft/venting issue).	New filter; clear intake/exhaust; verify inducer and tubing. Tech to check switch set-point and vent lengths.
E240	Limit switch circuit open (overheat).	Replace filter, open vents, verify blower speed/profile. Repeats: tech to measure temp rise/airflow and assess limit.
E270	Flame not detected.	Clean/replace flame sensor; verify igniter and gas pressure. Tech to confirm flame current/ignition sequence.
E 275	Flame detected out of sequence.	Inspect burner assembly for debris/misalignment; tech to test gas valve leakage and sensor wiring.
E290	Indoor blower motor temperature too high.	New filter, clear returns/vents, clean blower wheel. Tech to check amps/bearings and airflow.
E 292	Restricted airflow.	Replace filter first; inspect ducts for collapses/obstructions. Tech to measure static, adjust blower taps, add returns.
E 407	Compressor start winding open (outdoor unit tie-in).	High-voltage diagnostics only—book a pro to test capacitor/windings and repair the outdoor unit.

If a code returns immediately after the quick checks—or involves limit, rollout, gas valve, or motor overheat—book furnace repair Toronto right away.

Why these codes happen (and how pros fix them)

Airflow & Overheat (E 240, E 290, E 292)

Clogged filters, crushed flex, closed registers, or undersized returns push static pressure up and trip limits. Pros measure static pressure, verify temperature rise, right-size filter cabinets/returns, and set blower ramps for quiet, steady heat.

Ignition & Flame (E 270, E 275)

Weak/dirty flame sensors, aging igniters, or gas valve issues cause failed or out-of-sequence ignition. Techs check flame current (µA), burner alignment, and manifold pressure; they clean burners and replace worn parts.

Venting/Draft & Pressure Switches (E 223)

Blocked intake/exhaust, condensate in pressure tubing, or inducer faults open the switch. Expect a termination check, tubing purge, inducer test, and vent pitch/length corrections.

Power & Controls (E 105, E 110, E 201, E 125)

Loose low-voltage wiring, brownouts, failed sensors, or miswired valves trigger these. Pros validate line voltage, inspect harnesses, update firmware where applicable, and replace sensors/boards.

Outdoor Unit Tie-ins (E 407)

Communicating systems can surface outdoor faults on the furnace controller—strictly pro territory due to high voltage and refrigerant.

DIY That’s Safe (and actually useful)

Filters: set reminders; keep spares for winter.
Returns: vacuum grilles; don’t block with furniture/boxes.
Condensate: eyeball traps/hoses for kinks or algae during filter changes.
Thermostat: ensure staging/fan profiles match your furnace after any thermostat swap.

When to stop troubleshooting

Gas/rollout/limit codes or repeated lockouts
Electrical smells, tripping breakers, melted insulation
Not comfortable using a multimeter or accessing the blower

At that point, book professional furnace repair Toronto (and yes, searches for furnace repair GTA will find us too). We diagnose, repair, and reset safely—with clear pricing and same-day options across the GTA.

Service Area & Quick Links

City / Area	Learn More
Furnace Installation Mississauga	Visit page
Furnace Installation Markham	Visit page
Furnace Installation East York	Visit page
Furnace Installation Ajax	Visit page
Furnace Installation Greater Toronto Area	Visit page

FAQ: Lennox Furnace Error Codes (Toronto Homeowner Guide)

Q1. What does Lennox Error Code E 105 mean?

E 105 signals a device communication problem on the RS-Bus — the furnace control isn’t “talking” to other devices (e.g., thermostat). Reseat low-voltage wiring at the board/thermostat and check for damaged harnesses. If it returns, book a pro to test the control bus and board.

Q2. What is Error Code E 110 (low line voltage)?

E 110 means the unit detected low supply voltage. Check the breaker and shared circuits; if you have a multimeter, confirm stable voltage. Persistent low voltage needs an electrician or HVAC technician.

Q3. What does Error Code E 201 indicate?

E 201 usually means the outdoor air temperature sensor failed or is unplugged. Inspect wiring; replacing the sensor typically resolves it. Call a certified tech if you’re unsure.

Q4. What is Error Code E 223 and is it dangerous?

E 223 indicates a hard lockout related to the rollout circuit opening (or having been open). Shut the system off. Possible causes include a blocked vent, improper gas pressure, or burner flame rollout. Have a licensed technician inspect the rollout switch, burners, and venting.

Q5. What causes Error Code E 292 (restricted airflow)?

E 292 points to restricted airflow — most often a dirty filter, blocked return/supply, collapsed flex, or blower issues. Replace the filter first; if airflow’s still weak, have a pro check ducts and blower alignment.

Q6. What does Error Code E 240 (limit switch open) mean?

E 240 means the limit circuit is open, usually from overheating due to poor airflow. Install a clean filter, open all vents, and ensure returns aren’t blocked. If it repeats, a technician should verify temperature rise, blower settings, and the limit switch.

Q7. What is Error Code E 407 (compressor start winding open)?

E 407 indicates the compressor’s start winding circuit is open (on systems paired with AC/heat pump). This is high-voltage work — book an HVAC professional to test the capacitor/windings and repair safely.

Need help now?

If your Lennox keeps throwing codes—especially E 240, E 270, E 275, E 292—don’t keep resetting. Book furnace repair Toronto with For Saving Home Services Inc for diagnostics, clean repairs, and reliable heat tonight.