Lennox ML193UHE furnace 2 red flashes: Improper Earth Ground
Professional repair
What do 2 red LED flashes mean on a Lennox ML193UHE with ignition control 103217-03? The ignition control has detected an improper earth ground at the furnace. The code reports the electrical condition the board sees; it does not identify where in the circuit the ground is missing.
Before you touch anything: the six signs that mean stop troubleshooting and call a pro →
Ground-path testing involves line-voltage wiring and should be done by a licensed technician or electrician. Do not open the control compartment or alter grounding connections yourself.
Possible causes
- Loose, missing or faulty earth ground connection for the furnace TECH
Parts for this code
No model-verified part number is listed here. Have the fault diagnosed and the correct part matched to your furnace before ordering.
Questions about this code
What do 2 red LED flashes mean on a Lennox ML193UHE with ignition control 103217-03?
The ignition control has detected an improper earth ground at the furnace. The code reports the electrical condition the board sees; it does not identify where in the circuit the ground is missing.
How do I fix Lennox ML193UHE furnace 2 red flashes?
Schedule electrical diagnosis rather than restarting the furnace repeatedly. Write down the flash count and what the furnace was doing. The technician traces the ground path from the board to the supply and repairs the connection that is missing or poor.
How much does it cost to fix Lennox ML193UHE furnace 2 red flashes?
Cost depends on diagnostic time and where the ground fault sits. A problem at the furnace connection and one in the building wiring involve different amounts of labor.
Applies to
ML193UHE
Different Lennox generations use different code maps. If your series isn't listed, don't assume this meaning — check your blower-door label.
Verified against Lennox ML193UHE Installation Instructions, p.39
Verified against Lennox ML193UHE Unit Information / Service Literature, p.9
Last verified 2026-10-07 · page updated 2026-10-07 · how we verify
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