Lennox EL296UHV Error Code E 204: Gas Valve Mis-Wired
What Does Code E 204 Mean?
Error code E204 on the Lennox EL296UHV indicates that the control board has detected incorrect wiring on the gas valve. The board performs a pre-ignition check of the gas valve circuit and has found that the wiring does not match the expected configuration.
This code most commonly appears after a gas valve replacement, a control board replacement, or other service work where the gas valve wiring was disturbed. Incorrectly wired gas valve connections can cause the valve to operate erratically — potentially opening when it should be closed, or failing to open when commanded. Either condition is a safety concern.
The error clears when the wiring is corrected. A qualified HVAC technician must inspect the gas valve wiring against the furnace wiring diagram and correct any mis-wired connections before the furnace can be safely operated.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Incorrect gas valve wiring connections | Most common | ✗ Call a pro → |
When to Call a Professional
Contact a licensed HVAC technician if:
- Immediately — gas valve wiring errors are a safety issue
- The furnace was recently serviced and E204 appeared afterward
- You smell gas near the furnace at any time
✓ Verified against manufacturer service manual — March 2026