Lennox Furnace 2 error code
Two flashes mean the furnace does not have a proper earth ground. Flame sensing depends on a good ground, so the control will not run the furnace reliably without one.
Also shown as: 2 flashes, two flashes, fault code 2, bad ground, improper ground
Last updated: September 30, 2026
What causes the 2 error?
- Ground wire loose, corroded, or disconnected
- Furnace not bonded to the home's grounding system
- Corroded grounding point
How to fix Lennox 2 — step by step
Work through these in order, from simplest and safest first. Stop as soon as the code clears.
- Call an electrician or HVAC technician
Verifying and repairing equipment grounding requires opening electrical compartments and testing with a meter.Safety warning: Never operate the furnace with a known bad ground, and never try to 'make' a ground with improvised wiring. This is licensed-professional work.
When to call a technician
- As soon as the code appears
- If you ever feel even a mild tingle touching the furnace cabinet — turn the breaker off and call immediately
Frequently asked questions
Why does a furnace need a ground to sense flame?
Flame rectification works by passing a tiny current from the sensor rod through the flame to the grounded burner. Without a solid ground, the control cannot confirm the flame and shuts down.
Is this urgent?
Yes. A missing equipment ground is both a shock hazard and the reason the furnace will not stay lit.
Sources
Every meaning and fix above was checked against official manufacturer documentation:
FixCode provides general troubleshooting information only — not professional repair advice. If you are unsure about any step, stop and call a qualified technician. Repairs done incorrectly can be dangerous and may void your warranty.