Lennox SLP98UHV Error Code E 228: Pressure Switch Calibration Failed
What Does Code E 228 Mean?
Because the SLP98UHV is a modulating furnace that changes its firing rate on the fly, the SureLight Variable Capacity Integrated Control cannot rely on a single fixed draft target the way a single-stage furnace can. Before it commits to a heat cycle, the control runs a pressure-switch calibration routine that learns the baseline draft references it will later use to prove venting at both the low-fire and high-fire rates. Error code E228 is set when that calibration routine cannot complete successfully.
When calibration fails, the control does not simply keep hammering the ignition sequence. It waits roughly 300 seconds (five minutes) and then attempts the calibration again. The internal error counter is cleared when the furnace exits the lockout state, so from the outside the furnace appears to sit idle, try again, and sit idle in a repeating pattern. If the calibration keeps failing across repeated attempts, the control escalates to E 276 (soft lockout after the calibration retry limit is exceeded), which stops the retries entirely until the fault is corrected.
E228 is a calibration fault, not a switch-state fault, so it is distinct from E 223 (the low-fire pressure switch failing to close) and E 225 (the high-fire pressure switch failing to close). Those codes report a specific switch that would not close on demand, whereas E228 means the board could not establish a stable, trustworthy pressure reference at all. The usual reasons are a pressure-sensing hose that is disconnected, cracked, or holding condensate, a loose or corroded pressure-switch wiring connection, or a vent condition that makes the draft pressure fluctuate so much that no stable baseline can be captured.
What You'll Notice
- The furnace never reaches ignition — the inducer may run, then everything goes quiet
- No heat, with the 7-segment display showing E 228
- A repeating pattern where the furnace tries, pauses for about five minutes, then tries again
- The house slowly cools because the burners are never allowed to light
- In some cases E 276 also appears in the code history after several failed attempts
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Pressure switch hose disconnected or cracked | Most common | ✗ Call a pro → |
How This Is Diagnosed
A technician starts by confirming the fault is calibration-related rather than a stuck switch, because that points the investigation at the pressure-sensing path rather than the burners or gas train. As a homeowner-safe first check, you can walk outside and inspect the exhaust and intake vent terminations for anything blocking them — ice, snow, leaves, insect or bird nests, or a screen packed with debris — since an unstable vent condition is a common reason calibration cannot settle.
From there the work belongs to a technician. They inspect the rubber pressure-switch hose between the inducer housing and the switch for cracks, kinks, a loose fit, or trapped water, check the pressure-switch wiring connections for looseness or corrosion, and measure the actual draft pressure in inches of water column against the switch specifications. They also confirm the combustion-air inducer is spinning up normally, since a weak or restricted inducer produces the same unstable readings that defeat calibration.
When to Call a Professional
This code involves components that are not homeowner-serviceable, so have a licensed HVAC technician diagnose and repair it. Keep in mind:
- The furnace repeatedly fails to start and keeps returning to E 228 after each five-minute pause
- E 228 appears together with E 276 in the code history
- You have already cleared the outdoor vent and intake terminations and the code persists
- You see or suspect water trapped in the pressure-switch hose or inducer housing
Frequently Asked Questions
Why does my SLP98UHV wait five minutes and then try again on its own?
That built-in delay is normal behavior for E 228. The control pauses about 300 seconds before re-attempting the pressure-switch calibration so it is not cycling continuously. It is not a sign that the problem has fixed itself — the underlying hose, wiring, or vent issue still needs attention.
Is E 228 the same as a bad pressure switch?
Not necessarily. E 228 means the control could not complete its calibration routine, which depends on the switch, its hose, the wiring, and a stable draft. The switch itself may be fine while a cracked hose or an unstable vent is the real cause. A technician isolates which part is at fault.
Can I just keep resetting the furnace at the breaker?
Cycling power will clear the state, but if the calibration keeps failing the furnace will return to E 228 and can escalate to the E 276 lockout. Because this code is tied to safe venting verification on a gas furnace, the root cause should be diagnosed rather than repeatedly reset.
✓ Verified against manufacturer service manual — March 2026