HeatingCodes

Lennox furnace diagnostic codes (SL280DFV)

By Jason Dearmin · Last reviewed November 14, 2026

Lennox furnaces with this integrated control show their status and faults on a seven-segment display on the control board. Codes that start with E are faults, and the manual says what clears each one.

What this table coversCodes from the Integrated Control Diagnostic Codes section of the Lennox SL280DFV installation instructions (508246-01, 04/2024). Older Lennox furnaces and other series can use different code lists.

How to read the display

Normal operation is shown with letters rather than codes. A blinking decimal point is idle mode. "H" is gas heat, "h" is heat pump stage, "C" is cooling, "d" is dehumidification and "dF" is defrost mode. A fault is shown as a letter E followed by three digits, such as E250.

In the Lennox table, the E1xx codes are mostly power, ground and communication faults, and the E2xx codes are furnace operation faults such as limits, pressure switches, flame and the blower. A soft lockout lasts one hour, and the manual says that for the codes below it "clears when heat call finishes successfully."

Lennox code table

CodeMeaningWhat the document says
E000 No error in memory
E105 Device communication problem, no other devices on RS BUS The manual says to separate high-voltage power from the RSBus wiring and check for miswired or loose connections between the thermostat, indoor and outdoor units. The fault clears after communication is restored.
E110 Low line voltage Voltage is lower than the nameplate rating. Check power line voltage and correct. The alarm clears 5 seconds after the fault recovers.
E111 Listed in the table as "Low line voltage"; the action given is to correct reversed line power wiring The system resumes normal operation 5 seconds after the fault recovers.
E112 Ground not detected The system shuts down. Provide proper earth ground.
E113 High line voltage Voltage is higher than the nameplate rating. Provide power voltage within the proper range.
E115 Low 24-volt power The range is 18 to 30 volts. The manual says to check for power-robbing equipment and that a larger VA transformer may be required.
E117 Poor ground detected (warning only) Provide proper grounding for the unit.
E124 Communicating thermostat signal missing for more than 3 minutes The equipment lost communication with the thermostat. Check the four wiring connections and cycle power at the thermostat.
E125 Control failed self-check, internal error Hardware problem on the control. Cycle power. Replace if the problem is persistent and prevents service.
E200 Hard lockout: rollout circuit open or previously open Correct the cause of the rollout trip, or replace the flame rollout switch. Test furnace operation.
E201 Indoor blower communication failure Lost communication with the indoor blower motor. The manual lists motor not powered or loose wiring.
E204 Gas valve miswired Check gas valve operation and wiring.
E205 Gas valve control relay contact shorted Check wiring on the control and gas valve. If wiring is correct, replace the control.
E206 Gas valve second-stage relay failure The furnace will operate on first stage for the rest of the heating demand.
E207 Hot surface igniter sensed open Measure igniter resistance and replace it if it is open or outside the specified range.
E223 Low pressure switch failed open Check the pressure at which the low pressure switch closes, then inspect the vent and combustion air inducer for correct operation and restriction. Full explanation
E224 Low pressure switch failed closed Check whether the switch is stuck closed on a heat call longer than 150 seconds.
E225 High pressure switch failed open Check the pressure at which the high pressure switch closes, and inspect the vent and inducer.
E226 High pressure switch failed closed
E227 Low pressure switch open during trial for ignition or run mode Full explanation
E228 Combustion air inducer calibration failure Unable to perform pressure switch calibration. Check the vent system and pressure switch wiring.
E229 Ignition on high fire The control switched to high-fire ignition because the low-fire pressure switch did not close in the allowed time. The manual says no action is needed.
E240 Low flame current, run mode Check flame sensor microamps. Clean or replace the sensor and check the ground. The alert clears after the heat call.
E241 Flame sensed out of sequence, flame still present Shut off gas. Check for a gas valve leak.
E250 Limit switch circuit open If the limit does not close within 3 minutes, the furnace goes into a 1-hour soft lockout. Full explanation
E252 Discharge air temperature too high (gas heat only) Check temperature rise, airflow and input rate.
E270 Soft lockout: exceeded maximum number of retries, no flame current sensed Check for proper gas flow, that the igniter is lighting the burner, and flame sensor current. Full explanation
E271 Soft lockout: last retry failed because the pressure switch opened Inspect the vent and combustion air inducer for correct operation and restriction. Full explanation
E272 Soft lockout: last recycle was due to the pressure switch opening Full explanation
E273 Soft lockout: last recycle was due to flame failure Check flame sensor microamps. Clean or replace the sensor. Full explanation
E274 Soft lockout: last recycle failed because the limit circuit opened, or stayed open more than 3 minutes 1-hour soft lockout. Check firing rate, airflow and blockage. Full explanation
E275 Soft lockout: flame sensed out of sequence Shut off gas and check for a gas valve leak. 1-hour soft lockout.
E290 Igniter circuit fault Measure igniter resistance. Replace if open or out of specification. 1-hour soft lockout.
E292 Indoor blower motor unable to start (obstructed wheel or seized bearings) 1-hour soft lockout. Clears after the blower successfully starts.
E295 Indoor blower motor temperature too high The motor tripped on its internal protector. Check bearings and amps.

Source: Lennox 508246-01 (04/2024), Integrated Control Diagnostic Codes. This is a selection of the heating-related codes in that table, not the full list.

Detailed explanations

SafetyThese tables describe what the manufacturer documents say. Gas, combustion, refrigerant and line-voltage repairs are for licensed professionals. If you smell gas, leave the building and call your gas utility or 911. Safety disclaimer.

Sources