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Lennox SL280UHV Furnace Codes
Other Lennox furnaces with the same style of integrated control use E-codes too, but check the installation instructions for your model.
| Code | Meaning | What to check |
|---|---|---|
| E000 | No error in memory. | |
| E105 | Communication problem: no other devices on the RS-BUS. | Communicating thermostat wiring (i, R, C). |
| E110 | Line voltage low. | Supply voltage under load. |
| E111 | Line voltage low, likely reversed line power wiring. | Check hot and neutral at the furnace. How to fix → |
| E112 | No ground detected; system shuts down. | Verify the ground to the furnace. How to fix → |
| E113 | Line voltage high. | Supply voltage. |
| E114 | Line frequency out of range (not 60 Hz). | Generator or supply problem. |
| E115 | 24 V power low. | Transformer and 24 V wiring, shorts loading the circuit. How to fix → |
| E116 | 24 V power high. | Transformer and supply voltage. |
| E117 | Poor ground detected (warning). | Ground connection. How to fix → |
| E120 | Unresponsive device (communicating systems). | Communicating wiring and devices. |
| E124 | Communicating thermostat signal missing for more than 3 minutes. | Thermostat wiring and power. |
| E125 | Control failed self-check or internal hardware fault. | Replace the integrated control. |
| E131 | Corrupted control parameters. | Reprogram or replace the control. |
| E150 | A2L refrigerant leak alarm. | Find the leak; the furnace runs the blower to dilute refrigerant. |
| E151 | A2L refrigerant sensor fault. | Sensor and its wiring. |
| E180 | Outdoor air temperature sensor failure. | Sensor and wiring (communicating systems). |
| E200 | Hard lockout: rollout circuit open or previously open. | Find the cause of the rollout trip before resetting. How to fix → |
| E201 | Indoor blower communication failure. | Blower motor wiring and motor. |
| E202 | Indoor blower motor does not match unit capacity. | Wrong replacement motor or setup. |
| E203 | Appliance capacity/size not programmed. | Program the unit size per the installation instructions. |
| E204 | Gas valve mis-wired. | Gas valve wiring. How to fix → |
| E205 | Gas valve control relay contact shorted. | Replace the integrated control. |
| E206 | Gas valve second-stage relay failure. | Furnace runs on first stage; replace the control. |
| E207 | Hot surface igniter sensed open. | Igniter and its wiring. How to fix → |
| E223 | Low pressure switch failed open. | Vent, intake, hoses, condensate, inducer. How to fix → |
| E224 | Low pressure switch failed closed. | Stuck switch or wiring short. How to fix → |
| E225 | High pressure switch failed open. | Vent, intake, hoses, inducer. How to fix → |
| E226 | High pressure switch failed closed. | Stuck switch or wiring short. How to fix → |
| E227 | Low pressure switch open during trial for ignition or run. | Vent, condensate trap, hoses. How to fix → |
| E228 | Combustion air inducer calibration failure. | Vent system and pressure switch wiring. How to fix → |
| E229 | Ignition moved to high fire because the low pressure switch closed late (no action needed). | |
| E240 | Low flame current in run mode. | Clean the flame sensor; check ground and gas pressure. How to fix → |
| E241 | Flame sensed out of sequence, flame still present. | Gas valve leaking through. How to fix → |
| E250 | Limit switch circuit open. | Airflow: filter, blower, ducts, coil. How to fix → |
| E252 | Discharge air temperature too high (gas heat). | Airflow and temperature rise. How to fix → |
| E270 | Soft lockout: maximum retries exceeded, no flame current sensed. | Gas supply, igniter, flame sensor. How to fix → |
| E271 | Soft lockout: maximum retries exceeded, last retry failed on pressure switch opening. | Venting and pressure switch. How to fix → |
| E272 | Soft lockout: maximum recycles exceeded, last recycle from pressure switch opening. | Venting, condensate, pressure switch. How to fix → |
| E273 | Soft lockout: maximum recycles exceeded, last recycle from flame failure. | Flame sensor, gas pressure, ground. How to fix → |
| E274 | Soft lockout: maximum recycles exceeded, limit opened or stayed open over 3 minutes. | Airflow. How to fix → |
| E275 | Soft lockout: flame sensed out of sequence, flame signal now gone. | Gas valve, flame sense wiring. How to fix → |
| E290 | Igniter circuit fault. | Igniter and wiring. How to fix → |
| E292 | Indoor blower motor can't start (obstructed wheel or seized bearings). | Blower wheel and motor. |
| E295 | Indoor blower motor temperature too high. | Airflow restriction, motor. How to fix → |
| E310 | Discharge temperature sensor failure. | Sensor and wiring. |
| E311 | Heat rate reduced to match indoor blower airflow (warning). | Restricted ducts or filter. How to fix → |
| E312 | Restricted airflow in cooling or continuous fan (warning). | Ducts, filter, coil. How to fix → |
| E313 | Indoor/outdoor unit capacity mismatch (communicating, warning). | |
| E334 | Y1 relay stuck on the integrated control. | Replace the control. |
| E347 | No 24 V on Y1 with a non-communicating outdoor unit; stage 1 relay failed. | Control relay, Y1 wiring. |
| E348 | No 24 V on Y2 with a non-communicating outdoor unit; stage 2 relay failed. | Control relay, Y2 wiring. |
| E370 | Interlock (door) switch open for 2 minutes. | Blower door and door switch. |
How to read the codes
- The display shows E plus a three-digit code. A blinking decimal point in idle is normal.
- To recall the last 10 codes: press and hold the diagnostic push button next to the display; release when 'E' shows. To clear them, select 'c' and press the button again while it flashes.
- E1xx codes are power and communication, E2xx are ignition, pressure switch, flame and limits, E3xx are airflow and cooling.
Codes point to a circuit, not a part. Test before replacing anything, and never jumper a limit, rollout or pressure switch to keep a furnace running. Gas and line-voltage work is for trained technicians.
Source: Lennox SL280UHV Installation Instructions 508245-01 (04/2024), Integrated Control Diagnostic Codes. The "meaning" column follows the manufacturer's wording; "what to check" is our field summary. Always go by the label on the furnace you're working on.
Related
- How to read furnace LED flash codes
- Furnace pressure switch troubleshooting
- Flame sensor microamps and cleaning
Other brands
- Lennox Merit ML180UH (80% single-stage)
- Carrier 58CVA / 58CVX (80% variable-speed two-stage)
- Rheem / Ruud R96V / 96MDV (96% two-stage communicating)
- Goodman / Amana GR9S80 / GD9S80 (80% single-stage)
- Trane / American Standard S9X1 / S9X2 / S9B1 (96% condensing)
- Goodman / Amana / Daikin GM9S96 / GC9S96 / GM9S92 (96% and 92% condensing, single-stage)
- Carrier 59TP6C two-stage condensing with InteliSense (Performance series)
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