Lennox SLP98UHV Error Code Two horizontal bars: Soft Disable
What Does Code Two horizontal bars Mean?
Two horizontal bars on the Lennox SLP98UHV's 7-segment display indicate soft disable mode. This happens when the iComfort communicating thermostat detects a device on the data bus that it does not recognize, and sends that device a command to sit in soft disable until it has been properly configured. The device is not broken — it has simply not been registered in the thermostat's device list yet.
On a communicating SLP98UHV system, the furnace, thermostat, and outdoor unit all share a single data bus. Whenever the hardware on that bus changes, the thermostat has to re-learn what is connected. Soft disable most commonly appears right after a control board, outdoor unit, or thermostat is installed or replaced. Because it is a configuration state rather than a hardware fault, it is the least severe member of the bus family: a step milder than E105 (the board sees no devices on the bus at all), E120 (a device is present but slow to answer polling), or E124 (the thermostat signal has gone missing for over three minutes).
Clearing it requires a technician to confirm the bus wiring is correct, cycle power to the system, and then walk the iComfort setup routine to register the device — typically Setup > System > Devices > Thermostat > Edit. Until that setup is completed, the unrecognized device stays disabled so it cannot operate uncontrolled.
What You'll Notice
- Two solid horizontal bars shown on the furnace control's 7-segment LED instead of a normal status indication
- The problem appeared right after a new control board, outdoor unit, or thermostat was installed or replaced
- The affected equipment does not run even though the rest of the system has power
- The iComfort thermostat prompts to set up or configure a system device
- No heating or cooling from the disabled component until setup is completed
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Thermostat does not recognize a device on the communication bus after installation or replacement | Most common | ✗ Call a pro → |
How This Is Diagnosed
A technician starts by confirming the communicating bus is wired correctly and that the new or replaced device is landed on the right terminals with correct polarity, since a mis-land can make the thermostat see a device it cannot identify. Power is then cycled so every device re-announces itself on the bus.
With wiring confirmed, the technician goes into the iComfort thermostat's device setup menu and runs the registration routine so the thermostat recognizes and configures the previously unknown device. The two bars clear once the device is successfully added to the system's device list.
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 system needs to be reconfigured through the iComfort thermostat setup menu
- Soft disable appeared after equipment was installed or replaced
- You do not have access to the iComfort thermostat's advanced setup menus
- The two bars remain after cycling power at the breaker
Frequently Asked Questions
Did I damage something when the new part was installed?
No. Soft disable is a configuration state, not a hardware failure. The thermostat simply has not been told to recognize the new device yet, so it holds the device inactive until setup is done.
Can I clear the two horizontal bars myself?
Clearing it requires the iComfort thermostat's advanced device setup menus, which are intended for the installer. A homeowner can safely cycle power at the breaker, but if the bars return the configuration should be completed by a technician.
Will the furnace still heat while it shows two bars?
The specific device that is in soft disable will not operate until it is registered. Depending on which device is unrecognized, that can prevent normal heating or cooling, so it should be reconfigured rather than left as-is.
✓ Verified against manufacturer service manual — March 2026