What This Error Means

The furnace control detects an inadequate or improper electrical ground. A reliable ground path is necessary for electrical safety and stable flame-rectification sensing.

Symptoms You May Notice

Intermittent ignition; weak flame signal; burners light and shut off; no-heat condition; grounding fault after electrical or furnace work.

Common Causes

Loose ground screw; missing equipment-ground conductor; corrosion; painted or dirty bonding surface; damaged ground wire; improper neutral-to-ground connection; poor building electrical ground.

Safe Troubleshooting Steps

1. Turn off power. 2. Visually inspect furnace ground connections for looseness, corrosion or damage. 3. Confirm the furnace cabinet and burner assembly are properly bonded. 4. A qualified technician or electrician should measure grounding continuity and voltage relationships and correct improper neutral-ground connections. 5. Recheck flame current after restoring the ground.

Parts Commonly Involved

Equipment-ground conductor; furnace cabinet; burner ground path; electrical panel; integrated furnace control; flame sensor.

When to Call a Technician

Yes. Grounding should be evaluated by a qualified HVAC technician or electrician.

Safety Notice

Do not operate equipment with a suspected grounding problem. Improper grounding can create shock risk and unreliable flame-safety operation.

Manufacturer Documentation