Lennox Furnace Error Code E112

E112 means the Lennox furnace control board has detected that a proper earth ground is not present on the electrical circuit supplying the unit. As a safety response, the furnace shuts down and will not operate until a valid ground connection is established. This is an electrical wiring issue, not an internal furnace component failure.

No. The E112 fault causes the furnace to shut down specifically because operating without a proper ground is an electrical safety hazard. Running appliances without a valid ground connection can increase the risk of electric shock and equipment damage. The grounding issue must be resolved before the furnace is put back into service.

The cost depends on what is causing the grounding problem. If only a loose terminal or disconnected wire needs to be secured, an HVAC technician service call may cost anywhere from $75 to $200 depending on your area. If new wiring or panel work is required, electrician costs can range from $150 to $600 or more depending on the scope of the work and local labor rates.

If you are comfortable working with residential electrical wiring and can safely inspect connection points at the furnace junction box and disconnect, you may be able to identify a loose or disconnected ground wire and reattach it. However, if the problem involves the electrical panel or requires new wiring to be run, a licensed electrician should perform that work. Always turn off power to the furnace at the breaker before inspecting any wiring.

Resetting the furnace will not clear the E112 error permanently if the underlying grounding problem has not been corrected. The control board checks for a valid earth ground during each startup sequence, so the fault will return immediately if the ground is still absent or defective. The error will only stay cleared after a proper ground connection has been established.