Lennox SLP98UHV Error Code E 228: Pressure Switch Calibration Failed
What Does Code E 228 Mean?
Error code E228 on the Lennox SLP98UHV indicates that the control board could not complete a successful pressure switch calibration. The SLP98UHV uses a calibration routine to establish baseline pressure readings before each heating cycle. When calibration fails, the furnace cannot verify that the venting system is operating safely.
The system will automatically retry after a 300-second (5-minute) waiting period. If repeated calibration attempts fail, the furnace will lock out. The error counter is cleared when the lockout period ends, and the system tries the calibration process again from scratch.
Calibration failures are typically caused by issues with the pressure switch wiring connections, a disconnected or cracked pressure sensing hose, or problems with the vent system that create unstable pressure readings. A technician should verify all pressure switch wiring is secure, check the pressure hose for cracks or disconnections, and inspect the vent system for partial blockages or leaks.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Pressure switch hose disconnected or cracked | Most common | ✗ Call a pro → |
When to Call a Professional
Contact a licensed HVAC technician if:
- The furnace repeatedly fails to start and shows E228
- You notice the inducer motor starts but the furnace never proceeds to ignition
- E228 appears alongside E272 or E276 (lockout codes related to pressure switch issues)
✓ Verified against manufacturer service manual — March 2026