What This Error Means

The furnace control detected voltage or an energized gas-valve circuit when the valve should have been off. This is treated as a serious control or wiring fault.

Symptoms You May Notice

Heating shutdown; immediate fault; burners may not be allowed to start; fault may remain after a power cycle; unusual gas-valve behavior.

Common Causes

Stuck furnace-control gas-valve relay; shorted wiring; incorrect field wiring; moisture or board damage; external voltage on the gas-valve circuit; defective gas valve or connector.

Safe Troubleshooting Steps

1. Turn off furnace electrical power and close the manual gas shutoff. 2. Do not continue resetting the furnace. 3. Inspect visible wiring for damage without energizing the unit. 4. A qualified technician should isolate the valve circuit, check for unintended voltage, inspect the control-board relay and verify the gas valve is not mechanically passing gas. 5. Replace defective components and perform a full leak and combustion test.

Parts Commonly Involved

Gas valve; integrated furnace control; gas-valve relay; wiring harness; transformer.

When to Call a Technician

Yes, immediately.

Safety Notice

Shut off furnace power and the manual gas supply. This fault can involve unintended gas-valve operation and should not be treated as a DIY repair.

Manufacturer Documentation