Goodman furnace E4: Flame detected when no flame should be present

E4 means the control is seeing flame at a moment when the gas valve should be shut. Either gas is still burning when it should not be, or the sensing circuit is reporting a flame that is not there.

Applies to: Goodman GMVC96, GMVM97, GCVC96, GCVM97 and Amana AMVC96, AMVM97 series gas furnaces with a two-character alphanumeric display.

What it means

The control watches the flame sensor continuously, not only during the burn. If it detects flame while the gas valve is commanded closed, it reports E4 and normally runs the inducer to purge unburned gas from the heat exchanger. This is treated seriously because one of the two possible causes is a gas valve that is not fully closing — gas entering the combustion chamber outside a controlled cycle. The other cause is electrical: a short in the flame sensor wiring produces a signal the control cannot distinguish from a real flame. Since it cannot tell them apart, it assumes the dangerous one, which is the correct behaviour.

Most common causes

A gas valve leaking through or not closing fully, leaving a small flame after the cycle ends.
A slow-closing gas valve, where flame lingers briefly after shutdown and is caught by the check.
A short to ground in the flame sensor wiring or at the sensor.
A chafed or damaged sensor wire touching the cabinet.
A failed control board misreading the flame signal.
Residual flame on a burner after the main flame is cut, which points at a burner or manifold problem.

How to diagnose it

Note whether the inducer runs continuously without the furnace heating. That accompanies this fault and is the control purging the heat exchanger.
Do not open the burner compartment to look for flame with the furnace powered. There is no safe homeowner check for this one.
Note any smell of gas — if there is one, stop and act on the fix below rather than continuing to diagnose.

How to fix it

If you smell gas: leave the building, do not operate any electrical switch, and call your gas utility's emergency line or the fire service from outside. Do not go back in to investigate.
With no gas smell, switch the furnace off at its service switch and leave it off until a licensed technician has seen it.
This fault is entirely technician work. It involves the gas valve and the flame-sensing circuit — the two parts of a furnace a homeowner should never work on.
Do not reset repeatedly to see whether it clears. If a valve is not closing, each reset is another chance for uncontrolled gas.

Notes

The wiring-short version is far more common than a leaking gas valve, and a technician usually finds it quickly. That does not make it safe to assume — the control cannot distinguish them, and neither can anyone without test equipment at the valve.

Sources

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.