Lennox Furnace Error Code E261

E261 indicates a soft lockout caused by exceeding the maximum number of startup retry attempts, with the final retry failing because the pressure switch opened. The pressure switch is a safety device that confirms proper airflow and draft through the venting system. When it cannot stay closed across multiple attempts, the furnace shuts down and logs E261. Diagnosis should start with the E223 pressure switch fault procedure.

Start by following the E223 diagnostic procedure, which addresses pressure switch faults step by step. Check for blocked vents, damaged pressure switch tubing, condensate drain clogs, and inducer motor performance. If the pressure switch itself has failed or the inducer motor is weak, those components will need to be replaced. A qualified technician with a manometer can verify whether the switch is opening due to actual low draft or a faulty switch calibration.

Repair costs vary widely depending on the root cause. Clearing a vent blockage or replacing a pressure switch hose is relatively inexpensive, typically in the range of $75 to $200 for a service call and minor parts. Replacing a pressure switch generally runs $150 to $350 including labor, while an inducer motor replacement can range from $400 to $900 or more depending on the model and labor rates in your area.

Because E261 is a soft lockout, the furnace will attempt to restart automatically after its waiting period without requiring a manual reset. However, if the underlying cause of the pressure switch opening is not resolved, the furnace will fail again and return the same code. A manual power cycle may clear the lockout temporarily, but a proper repair is needed to prevent recurrence.

The furnace has already shut itself down as a safety measure, so it will not operate normally while in lockout. Attempting to repeatedly reset the unit without diagnosing the cause is not recommended, as it can mask a venting problem that could affect combustion safety. Leave the furnace off and have the pressure switch and venting system inspected before returning the unit to service.