IdLGoodman · GM9S96 · Furnace

Goodman GM9S96 code IdL

Idle

Normal, not a fault

Quick answer

On Goodman GM9S96 (2020s), IdL is a normal display state, not a fault. The board is powered up, sitting at the factory idle screen, and waiting for something to ask it to do a job. Nothing has failed. On this platform a letter followed by another letter reads like an error to most people, which is why this gets searched as a fault when it is simply what a healthy idle furnace looks like. A first thing to check: Normal powered state with no active call.

Applies to: Goodman GM9S96; Goodman GM9S96 and GR9S96 alphanumeric codes · Furnace · 2020s
Type of code: Status or setup value; Urgency: nothing to fix
First safe check: Set the thermostat to heat and call for a few degrees. If the furnace starts and the display changes, there was never a fault.

Checked 2026-09-26

What IdL means on this model

The board is powered up, sitting at the factory idle screen, and waiting for something to ask it to do a job. Nothing has failed. On this platform a letter followed by another letter reads like an error to most people, which is why this gets searched as a fault when it is simply what a healthy idle furnace looks like.

Symptoms you will notice

Display stays on the same screen and nothing happens
Furnace responds normally to the thermostat
No other warning signs anywhere in the house

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:

Normal powered state with no active call
Thermostat not calling for heat or cool
Furnace has just been powered up and is finishing a self check

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.

Set the thermostat to heat and call for a few degrees. If the furnace starts and the display changes, there was never a fault.
Note that this display is often mis-transcribed in online posts as 1dL, I dL, or Id1. Read the characters off your own display rather than trusting a written code.

Do not do these

×Do not power the furnace off repeatedly to clear a screen that is not an error.

When to call a technician

Worth scheduling, and worth your own checks first

You can usually keep living with this for a short while, but it will not fix itself. Do the safe checks below first, because a tripped switch or a blocked airflow is a five-minute fix that would otherwise cost you a service call.

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.

Nothing to do. Check the thermostat first if the system is not responding to a call.

What it costs to fix

Parts

None.

Labor