Lennox E310 Error Code

What does Lennox E310 mean?

E310 indicates a discharge air temperature sensor (DATS) failure on a Lennox communicating system. The alert activates when the sensor reads a shorted or out-of-range resistance value — an open (disconnected) sensor does not trigger E310. The DATS is used for discharge air control and cutback logic. The alert clears 30 seconds after the condition recovers or after a system restart.

Symptoms

• E310 or 'Discharge Air Temp Sensor Problem' displayed on the thermostat.
• System may limit or adjust heating output based on a faulty temperature reading.
• Alert activates during Field Test mode if the sensor is out of range.
• No alert if the DATS is simply disconnected — only shorted or out-of-range values trigger E310.

Common causes

• Shorted discharge air temperature sensor producing an out-of-range resistance reading.
• Sensor resistance outside the valid temperature/resistance curve for the model.
• Damaged sensor harness with wires contacting each other or a grounded surface.
• Corroded or loose connector at the sensor plug.

Ask the AskWhiz AI about Lennox E310

AskWhiz

online

Hi — I'm the HVAC demo. Ask me anything in this domain.

What causes Lennox E310?Step-by-step fix for Lennox E310?Is Lennox E310 safe to ignore?

MessageHelp me troubleshoot Lennox E310

Diagnostic steps

1. Locate and inspect the DATS sensor and wiring

   The discharge air temperature sensor is mounted in the supply plenum or duct downstream of the indoor unit. Inspect the sensor body and harness for visible damage, kinking, or corrosion at the connector.

2. Measure sensor resistance and compare to the temperature/resistance chart

   Disconnect the sensor plug and measure resistance across the sensor terminals with an ohmmeter. Compare to the resistance-versus-temperature chart in the indoor unit installation instructions for the ambient temperature at the sensor location.

3. Check for shorts in the sensor wiring

   With the sensor disconnected, measure resistance between each sensor wire and ground. Any measurable continuity to ground indicates a wiring short that must be repaired or the harness replaced.

4. Replace the discharge air temperature sensor if out of specification

   If the sensor resistance is out of range for the measured ambient temperature, replace the sensor with the Lennox-specified part. Reconnect and restart to confirm E310 clears.

5. Note: DATS on damper control or EIM modules does not generate E310

   Per Lennox documentation, a discharge air temperature sensor connected to a damper control module or Equipment Interface Module will not generate alert code E310 — only the sensor wired to the indoor unit control triggers this code.

When to call a professional

If E310 persists after sensor replacement, the indoor unit control board may have a failed input circuit. Communicating control board replacement on SLP99UHV and similar variable-capacity furnaces requires reconfiguration of unit size codes and recommissioning — tasks that require dealer-level access to the thermostat configuration menus and a licensed technician.