Lennox furnace E163: Furnace control board failure

E163 means the control board itself has a problem preventing the furnace from operating properly. Lennox states this may require replacing the indoor unit control board.

Applies to: Lennox gas furnaces with a seven-segment diagnostic display on the control board, such as the ML193UHEK, per installation instructions 508565-01.

What it means

Most furnace codes report something the control has observed elsewhere in the furnace. This one is the control reporting on itself. Lennox's wording is that there is an issue with the furnace control board preventing proper operation, and that replacement of the indoor unit control board may be required. The fault clears when the controller operates normally, which means a board with an intermittent fault can log this and then appear healthy. That matters for diagnosis: a stored E163 on a furnace that is currently running is not a false alarm, it is an intermittent hardware fault, and those get worse rather than better.

Most common causes

A genuine hardware failure on the control board.
Damage from a power surge or a lightning event.
Heat damage, often secondary to repeated overheating from another fault.
Moisture or condensate reaching the board.
Age, since these are electronic assemblies with a finite life.

How to diagnose it

Use the code recall menu to see whether this has been logged more than once. The control stores the last ten codes and an intermittent board shows a pattern.
Note whether the furnace has had condensate leaks or repeated limit trips, both of which damage boards over time.
Note whether the fault followed a storm or a power event.
Confirm the 24 volt supply is healthy before condemning the board — a board misbehaving on low voltage is not a failed board.

How to fix it

Technician work. Replacing a furnace control board involves the gas valve circuit and every safety on the unit.
Have the supply voltage and grounding checked first. Both produce board-like symptoms, and both are cheaper to fix.
If the board is replaced, whatever damaged it should be found — a board that failed from condensate or overheating will take the new one with it.
The fault clears when the controller operates normally, so a clear display does not mean it is resolved.

Notes

A control board is one of the more expensive parts on a furnace. Ruling out voltage, grounding and moisture first is worth doing properly rather than quickly.

All codes for this manufacturer

Lennox furnace alert codes — every code, with what differs between models.

This code is not a homeowner repair. Faults in this group involve the gas valve, the burner compartment, or the heat exchanger — the parts whose failure can put combustion products, including carbon monoxide, into the air the house breathes. Do not reset it repeatedly to keep the heat on. Have it looked at by a licensed technician, and make sure there is a working carbon monoxide alarm on every level of the home, including the level the furnace is on.

Sources

Lennox ML193UHEK Installation Instructions 508565-01, May 2026 — Integrated Diagnostic Codes / Status of Equipment

This site is a reference, not a substitute for a licensed HVAC technician. Gas appliances can leak carbon monoxide and cause fire. Anything involving gas lines, the heat exchanger, or the flame sensing circuit should be handled by a licensed professional. Pages are written with AI assistance from the sources listed on each page and checked against them before publishing.