HVAC Code Lookup

Lennox Furnace Code 2

WarningShown as: 2 rapid flashes (1/2 second on, 1/2 second off), then the LED stays off for 3 seconds and repeats

The control does not see an acceptable earth ground. The SureLight flame-sensing circuit references chassis ground, so the furnace will not run without one.

Manual wording: “2 - Improper Earth Ground”

Documented for: ML180UHE, ML193UHE and other Lennox furnaces using SureLight integrated control 103217-03 or 107163-01

Likely causes, most common first

  1. Ground wire missing, loose or corroded at the furnace junction box
  2. Furnace chassis not bonded to a proper earth ground

What you can safely check yourself

  • Confirm the furnace disconnect switch and breaker are on
  • Turn the furnace power switch off for 30 seconds and back on once to see whether the code returns

When to call a technician

Establishing or repairing the earth ground is electrical work inside the unit. Have a licensed electrician or HVAC technician verify and correct the ground.

A Lennox furnace throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.

Sources

Other Lennox codes