Lennox SLP98UHV Error Code E 204: Gas Valve Mis-Wired
What Does Code E 204 Mean?
Error code E204 on the Lennox SLP98UHV indicates that the gas valve wiring is connected improperly. The control board has detected an abnormal electrical condition in the gas valve circuit that does not match the expected wiring configuration.
This is a serious safety concern because an incorrectly wired gas valve could potentially open when it should be closed, or fail to open when needed. The control board has shut down gas heating operations as a protective measure. This code most commonly appears after a gas valve replacement, control board replacement, or other service work where the gas valve wiring was disturbed.
Do not attempt to operate the furnace or rewire the gas valve yourself. Gas valve wiring errors involve components that control the flow of natural gas or propane, and incorrect connections can create dangerous conditions. A licensed HVAC technician must inspect and correct the gas valve wiring connections.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Gas valve wiring connected incorrectly during installation or service | Most common | ✗ Call a pro → |
When to Call a Professional
Contact a licensed HVAC technician if:
- This code appears at any time — gas valve wiring issues require immediate professional attention
- The code appeared after recent service work or a gas valve replacement
- You smell gas near the furnace
✓ Verified against manufacturer service manual — March 2026