Lennox Furnace Code E206: Gas Valve Relay Fix & Cost
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Lennox furnace code E206: what it means
Lennox Code E206 means the integrated control is reporting a second-stage gas valve relay failure on a two-stage furnace. On two-stage and modulating furnaces, the control energizes separate first-stage (low fire) and second-stage (high fire) circuits at the gas valve; E206 is the control’s report that the second-stage relay function has failed.
That is the extent of what the code itself tells you. It does not identify why the relay circuit failed — that is what the diagnosis below is for. Because the reported fault is inside the control and its low-voltage circuitry, E206 is pro-level work.
In practice the furnace may still light and run on first stage but will not deliver high fire. If the code clears on a power cycle and then returns on the next high-fire call, the underlying problem has not been fixed. Legend wording and reset behavior can vary by board revision — confirm against the label inside your unit.
Lennox furnace code E206: common causes, ranked by probability
These are the possibilities a technician works through. The code names the failed function, not the root cause.
- Failed second-stage relay / control board — the most common finding. Worn or damaged relay contacts, a failed driver circuit, or board damage from a voltage surge all end in the same repair: the integrated control board is replaced.
- Damaged or corroded gas-valve harness / connector — a poor connection or damaged insulation on the second-stage lead is checked and ruled out before the board is condemned. Repairable if the board itself tests good.
- Second-stage gas valve problem — the second-stage coil and the valve itself are tested to rule them out as a contributor. If the valve is at fault, it is replaced.
- Water or debris intrusion on the board — condensate leaks or rodent damage near the control can corrode the board and its connections.
How to fix Lennox furnace code E206: safe checks first
These are the only steps a homeowner should attempt. Do not open the burner compartment, remove interior panels, or touch wiring.
- Thermostat: Confirm it’s set to Heat and the setpoint is above room temperature. Replace the batteries if it’s battery-powered.
- Air filter: Replace it if it’s dirty. A clogged filter causes short-cycling and is worth ruling out regardless.
- Breaker / service switch: Cycle the furnace breaker and the switch on the unit once. This is your single allowed reset. If E206 returns, stop and call a pro.
- Vents and registers: Make sure supply and return registers are open and unblocked.
- Condensate line: On high-efficiency units, check the external drain line and trap outlet for a visible clog, and look for standing water on the floor around the unit. Do not open the cabinet or inspect anything near the control board yourself.
Do not repeatedly reset a furnace that keeps re-logging E206 — repeated resets will not repair the reported fault.
How a technician will diagnose it
A qualified tech will:
- Read the fault history on the control to see how often E206 has occurred and whether it’s intermittent or persistent.
- Inspect the gas-valve harness and connectors for corrosion, loose pins, or damaged insulation on the second-stage lead.
- Measure the second-stage output with a multimeter during a high-fire call to see whether the control energizes the circuit.
- Test the second-stage gas valve coil resistance to rule the valve in or out.
- Check incoming line and 24 VAC to confirm the control is getting clean, stable power.
- Confirm the control itself — if the harness and valve test good but the second stage will not switch, the integrated control board is condemned and replaced.
A good quote should identify which component failed — the board, the harness, or the valve — not simply swap parts blindly.
Symptom, cause and what to do
| Symptom | Likely cause | DIY action | Technician job |
|---|---|---|---|
| Furnace runs on low fire only, weak heat on cold days | Second stage not being energized | Verify thermostat and filter; one reset | Test second-stage output, replace control board if confirmed |
| E206 returns immediately after reset | Persistent relay/board failure | Stop resetting; call pro | Replace integrated control board |
| Intermittent E206, works some days | Loose or corroded harness, or intermittent board fault | Note frequency and dates for the tech | Inspect/repair gas-valve harness, retest second stage |
| E206 with no high fire | Possible second-stage valve or coil problem | None | Test coil and valve, replace if faulty |
| E206 after a water leak near the unit | Corrosion on the control or connections | Clear the external condensate blockage | Inspect for water damage, replace board if needed |
Lennox furnace code E206 repair cost
Honest US ranges, parts and labor combined:
- Diagnostic / service call: $90 – $190
- Gas-valve harness or connector repair: $150 – $350
- Integrated control board replacement: $450 – $1,200 — communicating (iComfort-capable) controls sit toward the upper end
- Two-stage gas valve replacement: $400 – $750
- DIY: $0 — the only free option is a single reset; there is no homeowner-installable part for this fault.
Board replacement is the most common outcome for a genuine E206. If your furnace is under Lennox parts warranty, the board itself may be covered, leaving only labor.
Related codes
Other Lennox code pages you may need. Check the meaning of each against the diagnostic legend inside your own unit, since wording varies by board revision:
- Lennox Code E204
- Lennox Code E205
- Lennox Code E115
Frequently asked questions
Can I fix Lennox Code E206 myself?
No. E206 is the control reporting a second-stage gas valve relay failure. Diagnosis and any repair require opening the cabinet and testing live circuits, which is licensed technician work.
Will my furnace still run with Code E206?
Often it will run on first stage (low fire) but cannot switch to second stage (high fire), so you may notice weaker heat on very cold days. Some units may stop heating entirely until repaired. Behavior varies by model and board revision.
Does Code E206 reset on its own?
Treat it as a fault that needs service. If it clears after a power cycle but comes back on the next high-fire call, the problem is still present and a technician needs to look at it.