EFGoodman, Amana, Daikin · GMVM96 · Furnace

Goodman, Amana, Daikin GMVM96 error code EF

Auxiliary input open

Goodman is the platform name, and your unit may not say it

Amana AMVM96 / ACVM96, Daikin GMVM96 platform are the same board with a different badge, so this page covers all of them. The fault, the checks and the parts are identical, which is why there is one page rather than one per brand.

Worth keeping an eye on

Quick answer

On Goodman GMVM96 (2010s), EF is a fault. It means auxiliary input open. A first thing to check: Loose or disconnected wire on the C wire or an add-on terminal.

Applies to: Goodman GMVM96; Goodman and Amana GMVM96, GMVM97, GCVM96 alphanumeric codes · Furnace · 2010s
Type of code: Fault; Urgency: Worth keeping an eye on
First safe check: Check that all wires are firmly seated at the control board terminals. A wire that works loose with vibration is common on these.

Checked 2026-09-26

What EF means on this model

A control input expects a signal from something the furnace is working alongside, such as a heat pump, a humidifier or a zoning panel, and that input is reading open. The furnace itself may run fine, which is why this often gets ignored until a heat pump stops producing heat.

Symptoms you will notice

Furnace runs but the auxiliary equipment never starts
Heat pump does not come in when the thermostat calls for heat
Humidifier or zone panel not responding
Code is present but the furnace still heats

Common causes

The code tells you what the control detected, not which part failed. These are the causes we see most often, roughly in order of likelihood:

Loose or disconnected wire on the C wire or an add-on terminal
Failed heat pump control board
Failed humidifier or zone module
Damaged terminal on the furnace control board

What you can safely check

These are homeowner-level checks. None of them need you to open a live electrical compartment or work on gas.

Check that all wires are firmly seated at the control board terminals. A wire that works loose with vibration is common on these.
Confirm the add-on is actually calling for heat when the thermostat does.

Do not do these

×Do not assume the furnace is fine because it still heats. On a heat pump setup, the aux input can be the reason you have no heat at all.

When to call a technician

No call needed yet, but write it down

Note the date and the exact code, and watch whether it comes back. If it turns into a repeat fault or starts affecting performance, that is when it becomes worth a technician.

This is a fuel-burning appliance, so treat anything involving a burner, gas valve or flue as technician work. If you smell gas at any point, leave the property and call the gas utility from outside rather than continuing to diagnose.
If the appliance has stopped mid-cycle, is making a noise you have not heard before, or smells burnt, stop reading here and call. Those are symptoms of something the fault code does not describe well enough.

Re-seating a loose terminal is fine. Replacing a control board is not.

What it costs to fix

Parts

Usually no parts. Wires and terminals, occasionally a new board.

Labor

Under an hour to diagnose.

DIY or technician