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Common Lennox fault codes with what each means, the likely cause, and what CANRO Heating & Cooling does to fix them. Servicing Lennox systems across Metro Vancouver since 1999.
Lennox SLP99V, EL296V, ML193E gas furnaces and XC25/XP25 A/C and heat pumps signal faults via LED blink codes on the control board (for older units) and iComfort display (for communicating systems). Below are the most common codes.
Important: One reset attempt is generally safe for transient faults. If the same code returns within minutes, stop resetting — the lockout exists to protect the heat exchanger, ignition system, and gas-valve safety circuit. Note the exact code and call CANRO at (604) 359-1081. We carry common Lennox parts in every truck — most code-triggered faults are resolved in a single visit.
What it means: Normal operation.
Common causes: Nothing.
What to do: None.
Reset guidance: n/a
What it means: High-limit switch tripped.
Common causes: Low airflow (dirty filter, blocked supply), closed registers, failed blower.
What to do: Replace filter; clear blocked registers; call if persistent.
Reset guidance: reset OK
What it means: Combustion air pressure switch did not close.
Common causes: Vent blockage, condensate ice in vent, failed pressure switch, failed inducer.
What to do: Inspect vent if safe; call CANRO.
Reset guidance: no
What it means: Stuck-closed pressure switch.
Common causes: Failed pressure switch, wrong wiring.
What to do: Switch replacement.
Reset guidance: no
What it means: Burner failed to light after attempts.
Common causes: Flame sensor fouling (most common — Lennox flame sensors need annual cleaning), ignitor, gas valve.
What to do: Flame sensor clean is a $200-$350 first-visit repair.
Reset guidance: one reset OK
What it means: Flame rod sensing flame when there should not be one.
Common causes: Failed gas valve, flame rod wiring.
What to do: Call CANRO.
Reset guidance: no
What it means: Internal 24V power supply fault.
Common causes: Failed transformer, short in low-voltage circuit.
What to do: Service required.
Reset guidance: no
What it means: Gas valve circuit fault.
Common causes: Failed gas valve or wiring.
What to do: Gas valve service.
Reset guidance: no
What it means: Communicating-system signal loss.
Common causes: Wiring fault, board fault, thermostat fault.
What to do: Service required.
Reset guidance: no
What it means: Inverter board, compressor, refrigerant.
Common causes: Communicating-system board faults; refrigerant-charge issues.
What to do: Specialized service.
Reset guidance: no
Note the exact code on your display, then call CANRO. Most Lennox faults are diagnosed and repaired on the first visit because we stock common Lennox service parts in every truck.
📞 Call (604) 359-1081 nowCANRO services Lennox premium furnaces, AC and heat pumps in every Metro Vancouver city — including same-day emergency response for no-heat, no-hot-water, and gas-leak situations. See our city-specific Lennox pages:
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This Lennox error code guide is maintained by the CANRO Heating & Cooling team based on 25+ years of Lennox install, service, and repair experience across Metro Vancouver. Codes and behaviour described match current model manuals. Last reviewed May 2026.
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