Lennox E271 Error Code

What does Lennox E271 mean?

E271 is a soft lockout indicating the furnace has exceeded the maximum number of low-pressure switch retry attempts during the ignition sequence. Unlike E270 (ignition retries), E271 specifically counts repeated failures where the low-pressure switch would not close — the inducer ran but could not produce adequate draft for ignition to proceed. The board enters Watchguard mode after reaching the retry limit.

Symptoms

• Furnace enters a soft lockout with E271 displayed after multiple inducer attempts fail to satisfy the low-pressure switch.
• Inducer motor starts and runs but ignition sequence never proceeds.
• No heat produced — system waits in Watchguard mode before retrying.
• E227 or E223 may also be logged in the fault history alongside E271.

Common causes

• Persistent vent blockage preventing the inducer from reaching low-pressure switch closing draft.
• Clogged condensate drain causing water to back up and consistently block draft during ignition attempts.
• Failing inducer motor or capacitor that consistently produces insufficient draft.
• Faulty low-pressure switch that will not close at the correct draft pressure across repeated attempts.

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Diagnostic steps

1. Clear Watchguard lockout by power cycling

   Turn the furnace disconnect off for 30 seconds, then restore power to allow the system to reset the retry counter and attempt another ignition sequence.

2. Inspect and clear vent pipes and condensate trap

   Check both intake and exhaust PVC pipes for blockage. Flush the condensate trap and verify free drain flow. Clear any obstruction before attempting another ignition.

3. Measure draft pressure during inducer run

   Connect a manometer to the inducer housing pressure tap. Verify draft reaches the low-pressure switch closing setpoint within the allowable ignition sequence time.

4. Test the low-pressure switch

   Apply the rated closing pressure to the switch with a manometer and verify it closes. A switch that will not close at the rated pressure requires replacement.

5. Inspect inducer motor and capacitor

   Check inducer motor current draw with a clamp meter and test the run capacitor with a capacitance meter. A weak capacitor or motor producing below-rated draft across all retry attempts is the root cause.

When to call a professional

E271 after a single vent-clearing event is a sign the underlying draft problem is persistent and mechanical. A licensed technician can perform a complete inducer system evaluation — motor RPM, capacitor condition, and pressure switch calibration — to identify why the low-pressure switch is consistently not closing and determine the correct repair.