Lennox Furnace Error Code 2+5

Code 2+5 means the high fire pressure switch has been sensed in the open position, indicating the furnace is not detecting adequate draft pressure during the high-fire heating stage. This is a safety fault that shuts down the furnace to prevent unsafe operation. The most common cause on an 80% furnace is a blocked or restricted exhaust vent. The furnace will not resume normal operation until the underlying cause is resolved.

Yes, this fault is related to combustion venting, which makes it an important safety issue. The furnace is designed to shut down when proper exhaust draft is not confirmed, preventing potential exposure to combustion gases indoors. Do not attempt to bypass or override this safety function. If clearing the vent does not resolve the fault, have a qualified technician inspect the system before continuing to operate the furnace.

Resetting the furnace will clear the displayed fault code temporarily and allow the furnace to attempt another startup cycle. However, if the underlying cause such as a blocked vent or a failed component has not been corrected, the furnace will detect the same fault condition and shut down again, logging the code again. A reset is a useful diagnostic step to confirm whether the problem is intermittent or persistent, but it is not a repair on its own.

Start by locating the exhaust vent termination on the exterior of your home and checking it for any blockages such as ice, leaves, or animal nests, then clear any obstructions you find. After clearing the vent, reset the furnace and allow it to attempt a full heating cycle. If the code returns, a technician should inspect the pressure switch hose, the inducer motor, and the pressure switch itself for faults that require hands-on diagnosis.

If the cause is simply a blocked exterior vent, the repair can be free or minimal cost. If the pressure switch requires replacement, parts and labor typically run in the range of $100 to $300 depending on the specific switch and local labor rates. Inducer motor replacement is a more significant repair, generally ranging from $300 to $700 or more including parts and labor. Getting a diagnostic call from a technician first is the best way to determine the actual repair scope and cost.