On the covered Lennox gas furnace, E117 means poor ground detected. This is a warning only and clears 30 seconds after the fault recovers. First, look for a loose or corroded ground connection at the furnace without opening it. Then: Lennox says to provide proper grounding for the unit and to check for a proper earth ground to the system.
Differential
Likely causes of “Lennox gas furnace code E117”, and how to tell them apart
- 1
A loose or corroded equipment ground
What separates it The warning appears and clears on its own about 30 seconds after the fault recovers
How to confirm A technician checks the ground lug and the green wire from the furnace to the panel
- 2
An incomplete earth ground to the system
What separates it The code follows new work, a panel change or a moved furnace
How to confirm Confirm the supply circuit has a ground that reaches the electrical panel
- 3
Moisture or a damaged wire at the control
What separates it The code appears in humid weather or after a leak
How to confirm Look for rust, a wet harness or a nicked ground wire
Before you touch a setting
Record this first — changing settings destroys the evidence
- When the warning first appeared
- Whether work was done on the furnace or the panel
- Whether the furnace still heats
- The furnace model from the label
Try in this order
0 of 6 completedWhat to do first
ReversibleLook for a loose or corroded ground connection at the furnace without opening it.
Correct only the documented fault domain
ReversibleLennox says to provide proper grounding for the unit and to check for a proper earth ground to the system.
Check the earth ground
ReversibleE117 is a poor-ground warning. Provide proper grounding to the furnace and the system; the warning clears 30 seconds after the fault recovers.
Check that the furnace still runs
ReversibleE117 is a warning, so heating may continue. Note whether it does.
Look at the power cord or the cable entry
ReversibleWithout opening the cabinet, check the switch, the visible wiring and the cabinet for signs of corrosion or damage.
Have the ground verified
ReversibleLennox says to provide proper grounding for the unit and to check for a proper earth ground to the system.
Model-specific
What is true of this model and not of its siblings
- Shown as
- E117 on the ignition control.
- Applies to
- Lennox EL296UHV(X) and furnaces using the 103130-XX control.
Stop boundary
When this stops being a self-service repair
- !Ground work is electrical work for a licensed technician
- !Do not touch the control board to check the ground
Evidence ledger
Sources behind this answer
Exact questions
Common questions
What does E117 mean on a Lennox gas furnace?+
Poor ground detected. This is a warning only and clears 30 seconds after the fault recovers.
Is Lennox E117 an error or a warning?+
It is a warning for poor ground detection, not a lockout, and it clears about 30 seconds after the ground is restored.
What causes a poor ground on a Lennox furnace?+
A loose or corroded ground connection or an outlet without a proper earth. A technician can test the ground and fix it.
Will E117 stop my furnace?+
It is a warning, and it clears 30 seconds after the ground is restored.
Can a power strip cause a poor ground warning on a Lennox furnace?+
A furnace should be wired to its own grounded circuit, not a strip or adapter; a missing or loose ground at the outlet or junction is what the warning reports.
How do I know if the ground fault is in the furnace or in the house wiring?+
You cannot tell from the display. A licensed electrician can test the outlet or the circuit's ground, and checking that the furnace is on its own grounded circuit is the first step Lennox points to.
Should I keep the furnace on while E117 shows?+
E117 is a warning that clears by itself 30 seconds after the fault recovers, so heat may still run, but a poor ground is a safety matter and should be checked soon.
Is E117 a lockout?+
No. Lennox lists it as a warning that clears 30 seconds after the fault recovers.
Can a bad ground be dangerous?+
A poor ground removes a safety path for electrical faults, so it is worth fixing even when the furnace heats.
Does the control need replacing?+
Not as a first step. Lennox points at the grounding of the unit and system.