Lennox SLP98UHV Error Code E 226: High Pressure Switch Failed Closed
What Does Code E 226 Mean?
Error code E226 on the Lennox SLP98UHV indicates that the high-fire pressure switch has failed in the closed position. The control board expects the high pressure switch to be open before the inducer motor starts. Finding it already closed signals a fault that prevents the furnace from safely starting.
The high pressure switch operates at a higher threshold than the low pressure switch and is used to verify adequate draft during high-fire operation. When the switch contacts stick or weld closed, the control board cannot verify that venting conditions are safe, so it locks out ignition as a precaution.
A technician will need to check the high pressure switch contacts for continuity and replace the switch if it is stuck closed. The pressure tubing and inducer motor should also be inspected to ensure no underlying conditions contributed to the switch failure, such as moisture in the tubing or excessive inducer vibration.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Pressure switch contacts stuck or welded closed | Most common | ✗ Call a pro → |
When to Call a Professional
Contact a licensed HVAC technician if:
- The furnace will not start and displays E226
- The code appeared suddenly with no prior venting issues
- Both E224 and E226 appear together, suggesting a broader pressure switch problem
✓ Verified against manufacturer service manual — March 2026