Lennox Error Code E205 indicates Gas‑valve control relay contact shorted. Start by checking the most common and safe items identified in the troubleshooting section. If the code returns after those checks, professional diagnosis is recommended.
Easy
Gas‑valve control relay contact shorted
Unknown
Short in control relay contact on gas valve
Check wiring on control and gas valve; if wiring is correct, replace control
Gas valve control relay, wiring, control board
Call an HVAC technician if the error persists after completing the recommended basic troubleshooting steps or if the system repeatedly locks out.
Disconnect power before inspecting the equipment. Never bypass safety devices or operate the system if you suspect unsafe conditions.
Learn more about the furnace components and operating conditions commonly associated with diagnostic error codes: