Lennox EL296UHV Error Code E 310: Discharge Error Temperature Sensor Failure
What Does Code E 310 Mean?
Error code E 310 on the Lennox EL296UHV indicates a discharge air temperature sensor failure. This sensor measures the temperature of the air leaving the furnace and entering the supply ductwork. The SureLight integrated control only posts E 310 when the sensor reads shorted or outside its valid range, so the code reflects a sensor or wiring problem rather than an actual overheating event.
The control uses discharge temperature to monitor how the furnace is performing and to support temperature-based checks. With the sensor reading invalid, it loses that specific input, but the furnace can still heat. How the code clears depends on the mode: in communicating mode it clears about 30 seconds after the fault recovers, while in non-communicating mode it clears after the current heat call completes.
Because E 310 is a temperature-sensing input fault, it is diagnosed the same way as the other sensor codes on this control: by comparing the sensor's measured resistance to the temperature/resistance chart in the installation instructions. It is distinct from E 180, which involves the outdoor temperature sensor, and it relates to the discharge-temperature information shown by the "U" display and to E 252 on the same board. Confirming and replacing the sensor is a technician task.
What You'll Notice
- The seven-segment LED shows E 310 while the furnace otherwise still runs
- Heating continues, since E 310 is a sensor fault rather than a shutdown
- The code may appear and clear as the furnace cycles, depending on mode
- You may also see the discharge-temperature 'U' display or related sensor codes
- No obvious change in comfort, because the furnace keeps heating
How This Is Diagnosed
A technician measures the discharge air temperature sensor's resistance and compares it to the temperature/resistance chart in the installation instructions. A shorted or out-of-range reading confirms the sensor itself has failed, which is the most common reason for E 310.
They also inspect the sensor's wiring and connector, since a pinched wire or corroded connection can make a good sensor read out of range. If the sensor is confirmed out of spec, it is replaced to restore the discharge-temperature input.
When to Call a Professional
This code involves components that are not homeowner-serviceable, so have a licensed HVAC technician diagnose and repair it. Keep in mind:
- E 310 stays on or keeps returning as the furnace cycles
- The discharge-temperature 'U' display or E 252 also appears
- You want the furnace's supply-air temperature monitoring restored
- The sensor or its wiring needs to be measured against the resistance chart
- The code appeared after work near the supply plenum or sensor wiring
Frequently Asked Questions
Will the furnace still heat with E 310?
Yes. E 310 is a sensor input fault, not a safety shutdown, so the furnace continues to heat. It just loses the discharge-temperature reading the control normally uses for monitoring.
Why does it clear differently depending on mode?
In communicating mode the code clears about 30 seconds after the sensor reading recovers, while in non-communicating mode it clears after the current heat call finishes. Both simply reflect the sensor returning to a valid range.
How is E 310 different from E 180?
E 310 is about the discharge (supply) air temperature sensor inside the furnace. E 180 involves the outdoor temperature sensor. They are separate inputs, so they are diagnosed and replaced independently.
✓ Verified against manufacturer service manual — March 2026