Goodman furnaces communicate faults through a diagnostic LED located inside the unit, visible through the small sight glass on the furnace access panel. When a fault occurs, the LED flashes a pattern that corresponds to a specific fault code. This guide covers the most common Goodman error codes for the GMSS96, GMVC96, GMVC98, and similar models.
How to Read Goodman LED Flash Codes
Watch the LED light through the sight glass. It will flash a number of times, pause, then repeat. Count the flashes in the first sequence — this is your fault code. Most Goodman furnaces use a 2-digit code system: the first sequence of flashes is the first digit, a brief pause, then a second sequence for the second digit. The fault code chart is also printed on the inside of the furnace access panel door.
Goodman Furnace Error Code Chart
| Flash Code | Fault Description | Common Causes |
|---|---|---|
| Steady ON | Normal operation — no fault | N/A — furnace running normally |
| Steady OFF | No power or furnace off | No power, switch off, breaker tripped |
| 1 Flash | Rollout switch open | Flame rollout, heat exchanger crack, blocked flue |
| 2 Flashes | Pressure switch stuck open | Blocked intake/exhaust, faulty inducer, clogged condensate |
| 3 Flashes | Pressure switch stuck closed | Stuck switch, wiring issue |
| 4 Flashes | High-limit device open | Dirty filter, blocked return air, failed blower |
| 5 Flashes | Flame sensed without ignition call | Gas valve leaking, stuck open |
| 6 Flashes | Low flame sense signal | Dirty flame sensor, failing sensor |
| 7 Flashes | Ignition lockout — failed to light | No gas, faulty ignitor, dirty burners |
| 8 Flashes | Inducer or blower fault | Failed inducer motor, wiring issue |
| 9 Flashes | Reversed line voltage polarity | Wiring error at furnace or circuit breaker |
| Continuous Fast Flash | Control board fault | Failed control board |
Most Common Fault Codes Explained
2 Flashes — Pressure Switch Open
This is one of the most frequent Goodman fault codes. The pressure switch verifies that the inducer (draft motor) is creating proper airflow before allowing ignition. A pressure switch open fault means the switch didn't close. Check: are both PVC intake and exhaust pipes clear of ice or debris? Is the condensate drain flowing freely? Is the inducer motor spinning? See our full guide on furnace pressure switch diagnosis and testing.
4 Flashes — High-Limit Open
The high-limit switch cuts the burners if the heat exchanger gets too hot. Almost always caused by restricted airflow — check and replace the air filter first. Also verify all supply registers and return air grilles are open and unobstructed. A failed blower motor can also cause this. See our guides on furnace filter types and blower motor failure.
7 Flashes — Ignition Lockout
The furnace attempted to ignite multiple times and failed, entering lockout mode. The control board will not try again until reset. Common causes: no gas supply (check the gas valve is open and other appliances work), failed hot surface ignitor, or a dirty flame sensor that can't confirm ignition. See our guide on furnace ignitor types and replacement. Reset by turning the thermostat off for 30 seconds then back to heat.
6 Flashes — Low Flame Sense Signal
The flame sensor detects the burner flame to confirm ignition. If it's coated with oxidation, it can't sense the flame properly and shuts the furnace down. Cleaning the flame sensor with fine steel wool or emery cloth is a common DIY fix — it's a metal rod in the burner assembly, accessible after removing the furnace panel.
1 Flash — Rollout Switch Open
This is a serious fault. The rollout switch trips when flame is detected outside the combustion area — a significant safety event. This often indicates a cracked heat exchanger or blocked flue. Do not bypass this switch. Have a technician inspect before restarting. See our guide on cracked heat exchanger signs and replacement.
Resetting a Goodman Furnace After Lockout
After addressing the underlying cause, reset the furnace by: turning the thermostat down/off for 30 seconds, then setting it back to heat above room temperature. Some models also have a reset button on the burner assembly. If the furnace locks out again immediately after reset, do not keep resetting — call a technician.
Flame Sensor Cleaning: DIY Step-by-Step
- Turn off the furnace at the power switch and thermostat
- Remove the furnace access panel
- Locate the flame sensor — a metal rod mounted near the burner, with a single wire connector
- Remove the mounting screw and unplug the wire
- Lightly rub the metal rod with fine steel wool or 220-grit emery cloth until it's clean and shiny
- Reinstall and reconnect
- Restore power and test
This resolves code 6 (low flame sense) in the majority of cases and is safe for most homeowners to perform.
When to Call a Technician
Call a professional for: code 1 (rollout — possible cracked heat exchanger), code 5 (gas valve stuck open), code 9 (reversed polarity — electrical issue), continuous fast flash (control board failure), or any code that returns immediately after addressing the obvious cause. For winter emergencies, see our guide on what to do when your furnace goes out in Minnesota.
Need a New Goodman Furnace?
If your Goodman is aging and fault codes are becoming frequent, browse our Goodman furnace collection at Furnace Direct — factory-direct pricing with same-day Minnesota delivery and lifetime heat exchanger warranty.
Also see: furnace not turning on checklist and furnace short cycling causes and fixes.
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