Lennox Furnace Error Code E221

E221 means the low pressure switch has failed to close or has opened unexpectedly during a heating call. This switch monitors the negative pressure created by the inducer motor to confirm proper draft conditions before allowing the furnace to continue the ignition sequence. When the control board does not detect switch closure, it locks out the furnace and displays E221. The fault points to a venting issue, inducer problem, or a faulty pressure switch.

No. The E221 lockout exists specifically to prevent the furnace from operating under conditions where combustion gases may not be properly exhausted. Running the furnace while this fault is present could create a risk of carbon monoxide buildup inside the home. The system should remain off until the underlying cause is identified and corrected.

Repair costs vary depending on the root cause. Clearing a blocked vent or intake pipe may cost only a service call fee, typically in the range of $75 to $150. Replacing a defective low pressure switch is generally a lower-cost repair, often ranging from $100 to $250 including parts and labor. Inducer motor replacement is more involved and can range from $300 to $600 or more depending on the specific motor and local labor rates.

Some causes of E221 are accessible to a knowledgeable homeowner, such as clearing a blocked vent termination, removing ice from the intake pipe, or draining a clogged pressure switch hose. However, measuring water column pressure at the switch port, evaluating inducer motor performance, and replacing components require tools and skills that typically call for a qualified HVAC technician. If basic visual checks of the venting do not reveal an obvious blockage, professional diagnosis is recommended.

A reset may temporarily clear the code and allow the furnace to attempt another heating cycle, but E221 will return if the underlying problem has not been resolved. If the venting restriction, inducer issue, or failed pressure switch is still present, the control board will detect the open switch again and re-enter lockout. Resetting is useful for confirming whether the fault is intermittent, but it is not a repair.