Goodman furnaces report faults with an LED on the control board, usually visible through a small window in the blower door. When the furnace shuts down, the board flashes a code that points to the fault. Here is what the common codes mean on typical single-LED Goodman boards, and what is safe to check yourself.
How to Read a Goodman Error Code
On common Goodman single-LED control boards, the LED flashes a set number of times, pauses, then repeats. Count the flashes between pauses. A steady LED (on, not flashing) means normal operation, and a rapid continuous flash means the line-voltage polarity is reversed. Codes can differ between control board versions and models, so the code chart on the inside of the furnace door is the authoritative reference for your unit.
Goodman Furnace Flash Code Reference Chart
| Flash Code | Fault Description | Common Cause | DIY Possible? |
|---|---|---|---|
| 1 Flash | Lockout after failed ignition attempts | No gas supply, failed hot surface igniter, or a flame sensing problem | Confirm the gas valve is open and power-cycle once; call if it returns |
| 2 Flashes | Pressure switch stuck closed | Failed pressure switch or a wiring fault | Call a technician |
| 3 Flashes | Pressure switch stuck open | Blocked vent or intake, failed inducer motor, blocked or cracked pressure hose, or frozen condensate | Check outdoor vent pipes for snow or ice; otherwise call |
| 4 Flashes | Open high-limit switch | Restricted airflow: clogged filter, closed or blocked vents, or a blower problem | Replace the filter; call if it repeats |
| 5 Flashes | Flame sensed with no call for heat | Usually a gas valve that is not closing fully | Gas safety issue: turn the furnace off and call a technician |
| Steady On | Normal operation | No active fault | No action needed |
| Rapid Flash | Reversed line-voltage polarity | Wiring fault at the furnace power supply | Call a technician or electrician |
4 Flash Code: The Most Common Goodman Error
The 4-flash high-limit code is by far the most common Goodman fault call we receive. The limit switch is a safety device that shuts off the burners when the heat exchanger gets too hot. It trips when airflow through the furnace is restricted, usually by a clogged filter. Before calling a technician, replace your filter. If the furnace resets and runs normally, you have found and fixed the problem. If it trips again within a day or two, the problem is bigger: a failing blower motor, a blocked duct, or a collapsing return air duct.
1 Flash Code: Ignition Lockout
After a set number of failed ignition attempts, the board locks out and flashes once. Confirm the gas valve beside the furnace is open and that your other gas appliances work. You can clear the lockout once by turning the furnace power switch off for 30 seconds and back on. If it locks out again, the cause is usually a failed igniter, a dirty or failing flame sensor, or a gas supply problem. Flame sensor cleaning and igniter replacement mean working inside the burner compartment, so leave them to a licensed technician.
Goodman Model-Specific Notes
- Single-stage and two-stage models (such as GMSS96 and GMEC96): Typically use a single LED with flash codes. Check the chart on the blower door for your board version
- Modulating and communicating models (such as GMVM97): Can show more detailed fault information on the board or a compatible thermostat. Diagnosis on these models usually needs a technician
- Older 80% AFUE models: Flash code meanings can differ from current boards, so always use the chart on your furnace door
When to Call vs. When to DIY
You can safely replace the filter (4-flash), clear snow or ice from the outdoor vent pipes (3-flash), confirm the gas valve is open, and power-cycle the furnace once. Everything else, including flame sensor cleaning, igniter replacement, pressure switch faults, gas valve faults, and anything involving the heat exchanger, requires a licensed TSSA technician. Never bypass a safety control or reset a flame rollout switch yourself: doing so can result in carbon monoxide poisoning.
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Get Same-Day Goodman Furnace Repair?Frequently Asked Questions
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