Lennox SLP98UHV Error Code E 105: Device Communication Problem
What Does Code E 105 Mean?
Error code E105 on the Lennox SLP98UHV indicates a device communication problem — the furnace control board detects no other devices on the BUS communication system. The SLP98UHV uses a proprietary communication bus to exchange data with the iComfort thermostat, outdoor units, and other Lennox communicating components.
The most common cause is a loose or incorrectly wired communication connection. The communication wires run between the furnace, thermostat, and outdoor unit, and a single loose connection anywhere in the chain can break communication for the entire system. Wiring that was disturbed during maintenance, a rodent-chewed wire, or a corroded terminal can all cause this.
A less common but possible cause is electromagnetic interference from a nearby high-voltage source such as a welder, motor, or electrical panel. This type of noise can disrupt the low-voltage communication signal. The code clears when communication is re-established. A technician should inspect all communication wiring connections and check for sources of electrical interference near the system.
Common Causes
When to Call a Professional
Contact a licensed HVAC technician if:
- The communication wiring between system components needs professional inspection
- E105 appeared after recent service work or a storm
- Other system components (thermostat, outdoor unit) are also showing communication errors
✓ Verified against manufacturer service manual — March 2026